SACRAMENTO, Calif — At least two shooters opened fire early Sunday in Sacramento in the city’s second mass shooting in five weeks, killing six people and wounding 12 others as bars closed for the night and crowds emptied onto downtown streets, police said.

Three men and three women were killed, Police Chief Kathy Lester said. Their bodies remained on the pavement hours after the gunfire erupted around 2 a.m. Police sought clues from a crime scene that stretched across multiple city blocks as they searched for the shooters.

At least four of the wounded were hospitalized with life-threatening injuries. Authorities have not offered a possible motive and have so far identified only one victim, 38-year-old Sergio Harris, without providing a cause of death.

His sister Kay Harris, 32, told The Associated Press just hours after the shooting that she had been asleep when a family member called to say they thought her brother had been killed. She said she thought Sergio Harris had been at the London nightclub, which is near the shooting.

Pamela Harris, Sergio Harris’ mother, told The Sacramento Bee the family had not heard from him since the shooting.

“We just want to know what happened to him,” she said early Sunday. “Not knowing anything is just hard to face.”

Investigators pored through hundreds of pieces of evidence – much of it documented on the streets with blue and yellow markers – as officials begged the public to come forward with tips and videos that could help find the suspects.

Councilmember Katie Valenzuela, who represents the area, said she’s fielded many phone calls reporting violence in her district during her 15 months in office. She cried at a news conference as she told reporters that the latest phone call woke her up at 2:30 a.m.

“I’m heartbroken and I’m outraged,” she said. “Our community deserves better than this.”

Sunday’s violence was the third time this year in the U.S. that at least six people have been killed in a mass shooting, according to a database compiled by The Associated Press, USA Today and Northeastern University.

President Joe Biden called for action on gun crimes in a statement Sunday.

“Today, America once again mourns for another community devastated by gun violence,” Biden said. “But we must do more than mourn; we must act.”

Sacramento has endured two mass shootings in the last five weeks. On Feb. 28, a father killed his three daughters, a chaperone and himself in a Sacramento church during a weekly supervised visitation. David Mora, 39, was armed with a homemade semiautomatic rifle-style weapon, even though he was under a restraining order that prohibited him from possessing a firearm.

The area where Sunday’s killings occurred is on the outskirts of the city’s main entertainment district and has many bars and restaurants. It’s anchored by the Golden One Center that attracts big-name concerts and is home to the NBA’s Sacramento Kings. City officials have invested heavily in the area to promote development.

Videos on social media showed what appeared to be an altercation before the gunfire in California’s capital city. Sgt. Zach Eaton, a police spokesperson, said investigators don’t know if that fight led to the shooting.

Kelsey Schar was staying on the fourth floor of Citizen Hotel when she said she heard gunshots and saw flashes in the dark. She walked to the window and “saw a guy running and just shooting,” Schar told the AP.

Her friend, Madalyn Woodard, said she saw a crowd in the street scatter amid the gunfire and a girl who appeared to have been shot in the arm lying on the ground. Security guards from a nearby nightclub rushed to help the girl with what looked like napkins to try to stanch the bleeding.

A video posted on Twitter showed people running through the street amid the sounds of rapid gunfire. Nightclubs close at 2 a.m. and it’s typical for streets to be full of people at that hour in the city of about 525,000 people, located 75 miles (120 kilometers) northeast of San Francisco.

Pop duo Aly & AJ performed Saturday at Sacramento’s Crest Theatre and their tour bus was caught in the gunfire, the musicians said on Twitter. No one in their touring group was hurt, the tweet said.

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

“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,” he said.

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.

Mayor Darrell Steinberg said in recent years it “has been a very difficult time in downtown Sacramento,” as the city’s development efforts took a hit from the coronavirus pandemic.

He added that the shooting “gives pause to our entire community,” but he urged people to continue visiting the area.