SACRAMENTO, Calif (NewsNation) — Sacramento Police have arrested 26-year-old Dandre Martin in connection with a shooting in downtown Sacramento that left six people dead and at least 12 others injured, police announced Monday afternoon.

Police identified Martin as a “related suspect” and he was arrested and booked for assault and illegal firearm possession charges. It’s unclear if Martin will face additional charges.

Investigators said they recovered over 100 shell casings from the scene and at least three buildings and three vehicles were hit by gunfire. Police served search warrants at three residences in the area and at least one handgun has been recovered.

Police previously said they were searching for at least two people responsible for the deadly shooting but no other arrests have been made.

Three men and three women were killed in the shooting. The Sacramento County coroner identifed the three women who were killed as Johntaya Alexander, 21; Melinda Davis, 57; and Yamile Martinez-Andrade, 21. The three male victims were identified as Sergio Harris, 38; Joshua Hoye-Lucchesi, 32; and De’vazia Turner, 29.

Sacramento police Chief Kathy Lester said at a news conference Sunday that police were patrolling the area at about 2 a.m. when they heard gunfire. When they arrived at the scene, they found a large crowd gathered on the street and six people dead.

Investigators said they were reviewing video footage posted to social media that showed what appeared to be an altercation before the gunfire erupted.

Authorities say some victims either took themselves or were transported to hospitals. UC Davis Medical Center received four patients from the downtown shooting, spokesperson Stephanie Winn said. She declined to provide their genders or conditions.

Ten ambulances and 50 first responders from the Sacramento Fire Department responded to the shooting, according to Capt. Keith Wade.

This is “a very complex and complicated scene,” she said. Lester issued a plea to the public, asking for witnesses or anyone with recordings of the incident to contact police.

Gov. Gavin Newsom said in a statement that his administration was working closely with law enforcement.

“What we do know at this point is that another mass casualty shooting has occurred, leaving families with lost loved ones, multiple individuals injured and a community in grief. The scourge of gun violence continues to be a crisis in our country, and we must resolve to bring an end to this carnage,” he said.

Sacramento Mayor Darrell Steinberg expressed “shock and sadness” in a tweet Sunday, saying, “The numbers of dead and wounded are difficult to comprehend. We await more information about exactly what transpired in this tragic incident.”

“This is a senseless and unacceptable tragedy,” the mayor said during a news conference Sunday afternoon. “How many unending tragedies does it take before we begin to cure the sickness in this country? Let us be honest, this is a sickness.”

“The fact that we accept the idea that people can have ready access to assault weapons, to weapons of destruction, and can indiscriminately use them however and wherever they want” result in incidents such as Sunday’s, and “it happens far too often. It is a sickness in our culture and we must do everything we can to heal that sickness,” he said.

Shortly after the shooting, video was posted on Twitter that showed people running through the street amid the sound of rapid gunfire. Video showed multiple ambulances at the scene. Eyewitness accounts also depict a chaotic scene.

Residents were asked to avoid the area, which is packed with restaurants and bars. Nightclubs close at 2 a.m. and it’s normal for streets to be full of people at that hour.

Berry Accius, a community activist, said he came to the scene shortly after the shooting happened.

“The first thing I saw was, like, victims. I saw a young girl with a whole bunch of blood in her body, a girl taking off glass from her, a young girl screaming, saying, ‘They killed my sister.’ A mother running up, ‘Where’s my son, has my son been shot?’“ he said.

Kay Harris, 32, said she was asleep when one of her family members called to say they thought her brother had been killed. She said she thought he was at London, a nightclub at 1009 10th St.

Harris said she has been to the club a few times and described it as a place for “the younger crowd.”

The shooting was “very much …, a senseless, violent act,” she said.