(NewsNation) — Former President Donald Trump was the target of an assassination attempt at a Pennsylvania rally on July 13.

The FBI said that the attempted assassin was Thomas Crooks, a 20-year-old Pennsylvania man. The Secret Service shot and killed him seconds after Trump was shot. The attack was the most serious attempt to assassinate a president or presidential candidate since Ronald Reagan was shot in 1981.

Here’s what we know about the assassination attempt. You can watch the full report in the player above.

The Trump Assassination Investigation

The law enforcement failures didn’t just begin on July 13, the day of Donald Trump’s now infamous rally in Butler, Pennsylvania. They began weeks before, with what sources say, was a flawed plan by the United States Secret Service (USSS).

A source tells NewsNation the building that the gunman climbed atop to shoot the former president was supposed to be secured by local police. There was even a star on the plan, explicitly indicating it was the local police department that was responsible for securing the building — despite it being so close to where the president was speaking.

Sources say the USSS did not show up for the final planning meeting and their perimeter at the event was too small.

The Butler Township Police Department is small, with only 12 full-time officers amid a staffing shortage. NewsNation has learned a lieutenant is in charge following the chief’s retirement.

Sources close to the police department say they initially expected a department their size would be doing traffic and were surprised to learn that they would be in charge of securing the building along with a special local sniper team.

Concerns over security staffing at the Trump rally

Staffing concerns have come up again and again.

The Trump campaign had asked for additional USSS resources in the past. NewsNation has learned that on the day of the rally, the USSS requested an additional police unit outside the building. Butler Township says one was not available.

A source tells NewsNation that on the day of the rally, local police officers were inside the building and not keeping an eye on the roof.

Both federal and local sources agree local officers were on the roof briefly, but because of the heat, moved down to the ground. Another team of local officers was surveilling the building from the inside through a window.

Sources have told NewsNation from the beginning that there was a massive communication failure.

It may, however, be worse than previously realized.

The House Committee on Homeland Security says they’ve discovered that the USSS and local police were not able to talk to each other on their radios.

“Normally, they put a person from the locals in the Secret Service area,” said U.S. Sen. Mike Lee, R-Utah. “Today, the locals shared with us they were not allowed to have anyone in there. As far as radio communications, there was very little communication between the outer and inner perimeter.”

It appears it was rally attendees who spotted the gunman before police.

“A minute or two before the shooting, I saw a guy in a grey shirt climbing up the building beside us. I tried to alert cops. And then saw a rife slinging over his shoulder,” witness Jean Vincent said.

So why didn’t the Secret Service snipers take out the gunman before he started firing?

NewsNation obtained the below photo, with a time stamp of 6:04 p.m., seven minutes before the shooting. Snipers are seen looking in the direction of the gunman.

NewsNation also obtained a photo from 5:41 p.m. that shows snipers looking at the roof. Sources within the USSS say their current working theory is the sniper did not initially shoot Thomas Crooks because the sniper thought Crooks was a police officer on the roof.

This could stand to reason, given that the original security plan indicated local police were supposed to secure the roof.

Still, many warning signs were missed.

Body camera video after the shooting shows the confusion on the roof where the Secret Service and local police talk near the deceased gunman.

A congressional source who was briefed on the matter tells NewsNation that the shooter visited the rally site a few days prior to scope it out.

Crooks initially set off a metal detector at the rally because he had a range finder. The congressional source says 62 minutes elapsed between the time the shooter was photographed as being suspicious and when he fired the shots. Twenty minutes elapsed between the time snipers spotted him and when he fired the shots.

The Secret Service director says they were told about a suspicious person two to five times before the shooting but had no indication he had a weapon.

U.S. Secret Service Director Kimberly Cheatle resigned under pressure this week and acknowledged her agency failed in carrying out its plan to keep the former president safe.

The Gunman: Thomas Crooks

There is much we still do not know about the shooter but investigators are finding clues in his internet searches.

We know he had pictures on his phone of former President Trump, President Joe Biden and other officials including Attorney General Merrick Garland and FBI Director Christopher Wray. Investigators say he looked up the dates for the Democratic National Convention in Chicago along with Trump’s appearances.

There is still no clear motive of exactly why he wanted to kill Trump.

We are, however, getting a closer look at what may have led up that shooting. FBI Director Wray revealed disturbing new information about the suspected gunman.

“On July 6, he did a Google search for, ‘How far away was Oswald from Kennedy,’” said Wray, referencing the 1963 assassination of President John F. Kennedy in Dallas.

Wray told Congress that July 6, the day of that Google search, is the same day Crooks registered for the Butler, Pennsylvania, rally where he shot former president Trump and three others in the crowd.

“He was interested in public figures and, I think this is important, starting around July 6 or so, he became very focused on former president Trump and his rally.”

That focus turned into recognizance missions as he would go on to visit the fairgrounds six days before the rally.

Crooks, 20, worked at a nursing home where he washed dishes and served. He had no criminal record.

He bought the ammo for the assault rifle from a local gun store on the day of the shooting. Remote control devices attached to homemade bombs were found in his car but the bombs were left in the “off” position.

“We’ve recovered three devices, two in his vehicle and one back in his residence,” Wray told Congress. “I would say these are relatively crude devices but they did have the ability to be detonated remotely. There were receivers for those two devices with the devices and then on the shooter himself when he was killed by law enforcement he had a transmitter with him.”

A senior congressional source told NewsNation that Crooks had a “major depressive disorder diagnosis,” also known as clinical depression, a condition affecting 21 million U.S. adults, according to the 2021 National Survey on Drug Use and Health. His high school classmates say he was a “loner” and was ridiculed for the way he dressed.

“He was bullied,” a classmate told NewsNation. “He was bullied so much. You never think this would happen to you. But this is happening to me. I live here and this is happening. It’s so insane. You never know what the world is coming to these days.”

Wray described Crooks’ list of contacts as more limited than what one would expect and believes that he acted alone.

“So far — underline so far — we have not found any evidence of any co-conspirators, foreign or domestic.”

Full Timeline of the Trump Assassination Attempt on July 13

Earlier in the day, July 13

• Officials say Thomas Matthew Crooks bought 50 rounds of 5.56 mm ammunition for his AK-15-style rifle in Bethel Parks, Pennsylvania and drove north to Butler, the location of the Butler Farm Show where Trump was to hold a rally.
• Crooks, 20, parked at a gas station lot about one-third of a mile from the event.

Around 5 p.m.

• A young man is seen pacing around the edges of the rally area, looking at the buildings, acting suspiciously. Rallygoers capture his image in a cellphone video.

Around 5:20 p.m.

• Local law enforcement took notice of the man with a backpack and a range finder. They radioed their concerns and snapped a photo. But then the man vanished. The image was circulated by officers stationed outside the security perimeter.

Around 5:40 p.m.

• Local law enforcement spots the man again about 20 minutes before the shooting.

6:02 p.m.

• Trump takes the stage to the strains of “God Bless the U.S.A.” He waves at the cheering crowd and begins his regular rally speech, with spectators in front of him and behind him on risers.
• As Trump is speaking, Secret Service two-person sniper teams can be seen positioned on rooftops behind the stage, looking in opposite directions.

Around 6:09 p.m.

• Witnesses reported seeing a man climbing onto the roof of a one-story building closest to the stage. He then set up his AR-style rifle and lay on the rooftop, a detonator in his pocket to set off crude explosive devices that were stashed in his car parked nearby.
• Rallygoers yell to officers, pointing and shouting that an armed man had climbed to the roof of a nearby building. Witnesses capture his image in cellphone video.
• A local officer climbed to the roof, according to Butler County Sheriff Michael Slupe.
• A man identified by the FBI as Crooks turned toward the officer just before the officer dropped down to safety, Slupe said.
• Butler Township Manager Tom Knights said the officer lost his grip and was not retreating when he fell 8 feet to the ground.
• The roof where Crooks lay was an estimated 147 yards from where Trump was speaking.

6:11 p.m.

• Trump continued his speech and turned to his right to point toward a screen displaying border-crossing numbers when three shots were heard.
• As the first pop rings out, Trump says “Oh” and raises his hand to his right ear and looks at it, before quickly crouching to the ground behind his lectern.
• Secret Service agents rush to the stage and pile atop the former president to shield him. Rallygoers scream, crouch down and run away as heavily armed law enforcement officers surround the stage.
• Seconds after the first three shots, five more shots ring out in rapid succession.
• Corey Comperatore, a 50-year-old former fire chief attending the rally, is shot and killed. Pennsylvania Gov. Josh Shapiro said Comperatore used his body as a shield to protect his wife and daughter.
• Comperatore was seated in bleachers between where Crooks was positioned and where Trump was standing.
• Two spectators were critically wounded. One of the injured spectators was seated in the bleachers to the left of Trump as he faced forward. The bullet appeared to go past Trump, hitting the person.
• Other rallygoers and some law enforcement personnel suffered minor injuries from flying debris.
• Secret Service countersnipers fire back and fatally wound Crooks.

About one minute after the shooter is hit

• The Secret Service says the shooter is down.
• Video shows Trump getting to his feet and reaching with his right hand toward his face, which was smeared with blood.
• As Trump stands up, he pumps his right fist to the crowd.
• He appears to mouth the word “fight” twice to supporters, prompting loud cheers and then chants of “USA. USA. USA.”

About two minutes after the shots

• Trump turns back to the crowd and again raises a fist right before agents put him into a vehicle and take him to a local hospital.

6:50 p.m.

• Secret Service says, “The former President is safe.”

8:42 p.m.

• Trump posts on his social media site that he was wounded in the upper part of his right ear. “I knew immediately that something was wrong in that I heard a whizzing sound, shots, and immediately felt the bullet ripping through the skin,” he said.
• In a prime-time address, President Joe Biden urged the public to recommit to civil debate. Biden and Trump speak on the phone.

About 12:10 a.m., July 14

• Trump’s private jet lands at Newark Liberty International Airport.
• Video posted by an aide showed the former president deplaning, flanked by Secret Service agents and heavily armed members of the agency’s counterassault team. It was an unusually visible show of force by his protective detail.
• Trump travels to his private golf club in nearby Bedminster, New Jersey, to spend the night.