At least six people were killed and 12 people suffered “varying degrees of injuries” in a mass shooting in the center of Sacramento, California, early Sunday, police said.

Sacramento Police Chief Kathy Lester said at a news conference 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.

April 3, 202202:03

Authorities don’t know whether one or more suspects were involved. Lester issued a plea to the public, asking for witnesses or anyone with recordings of the incident to contact police.

This is “a very complex and complicated scene,” she said. Police later said that one firearm had so far been recovered at the scene.

The type of firearm or firearms used was not clear, but Sacramento Mayor Darrell Steinberg said during a news conference that there were “mass casualties in a very short period of time — that’s what we know.”

He called the shooting “a senseless and unacceptable tragedy.”

“Can we not have a sane debate where on one side of the line you say that people who want to use firearms for sport or for hunting or you know, with reasonable self defense on one side of the line and on the other side of the line, we say there is absolutely no place for rapid fire assault weapons anywhere anyhow,” Steinberg asked. “I mean, can we have that? Can we make that distinction?”

Sacramento City Councilmember Katie Valenzuela, through tears, said she was “heartbroken” and “outraged.”

“Our community deserves better than this. This is not unique to Sacramento, but we can stop it here,” Valenzuela said.

“Enough is enough. And I will travel wherever I need to travel and I will talk to whoever I need to talk to get these guns off our streets and to give our youth what they need so that they can be successful and that they don’t get shot down on K Street when they’re out trying to have a good time,” she said.

At about 9 a.m. local time, police said they were aware of a social media video that may show an altercation before the shooting. The department asked for those who were at the scene to share any related video they may have.

Video posted on Twitter showed people running through the street as the sound of rapid gunfire could be heard in the background.

Video also showed multiple ambulances had been sent to the scene. The shooting happened steps from city hall, in an area that is packed with bars, restaurants, hotels and museums.

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

“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.

City Hall was serving as an information center for families of victims, police said Sunday morning.

Steinberg wrote in a statement on Twitter: “Words can’t express my shock & sadness this morning. The numbers of dead and wounded are difficult to comprehend.”

“Rising gun violence is the scourge of our city, state and nation, and I support all actions to reduce it,” he added.

Gov. Gavin Newsom also released a statement, saying, “Sadly, we once again mourn the lives lost and for those injured in yet another horrendous act of gun violence.”

“As it is early in this investigation, my Administration will continue to work closely with local and state law enforcement as we monitor the situation,” he said. “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.”

Yuliya Talmazan and The Associated Press contributed.