(NewsNation) — A memo from the FBI and the Department of Homeland Security says that law enforcement should be concerned about more violence in response to the attempted assassination of former President Donald Trump. 

After the assassination attempt by 20-year-old Thomas Matthew Crooks, law enforcement is currently investigating the shooter’s motive. 

What did the memo say?

The memo sent to law enforcement said that there are ongoing concerns about retaliatory attacks following the assassination attempt. 

“We cannot rule out the possibility that some DVEs or other actors may attempt follow-on or retaliatory acts of violence in response to this assassination attempt,” the FBI and DHS said in a joint bulletin, using an acronym for “Domestic Violent Extremism.”

The two agencies also said that two improvised explosive devices were found in Crooks’ car and one in his home. 

“Over the last several months, Crooks received several packages, including some marked as possibly containing hazardous material, according to a review of his shipping history,” the bulletin read. 

The assassination attempt

Just a few minutes after Trump took the stage at a rally in Butler, Pennsylvania, shots were fired. Secret Service agents crowded around the former president and attempted to rush him off the stage. 

The local district attorney confirmed the shooter and one rallygoer were dead. The FBI identified Crooks as the shooter early Sunday. 

The other person who died was 50-year-old Corey Comperatore, a former fire chief. 

Police had received reports about a man pacing outside of the event’s metal detectors and witnesses also reported shouting about a man on a rooftop with a gun.  

The ongoing investigations

Following the assassination attempt, Trump’s campaign said he was “fine.” 

It is believed Crooks worked alone using a gun his father purchased, and bomb-making materials were found in his car. 

The FBI is investigating the attack as a potential act of domestic terrorism, but the motive has not yet been revealed. Analysts gained access to Crooks’ phone on Monday. 

The Secret Service plans to participate in an independent review following questions over how a gunman was able to get close enough to the president with an AR-style rifle to injure him, Director Kimberly Cheatle said in a statement. 

Congressmen Matt Gaetz and Jared Moskowitz have introduced a resolution honoring Comperatore for his sacrifice. The resolution calls on U.S. government officials to condemn the attempted assassination and other forms of political violence.