Police were looking for at least one suspect and had found at least one firearm.  Investigators said they were looking at videos posted on social media that showed what appeared to be a fight before the shootings broke out.
A video posted on Twitter showed people running down the street amid rapid gunfire in the city of about 525,000 people located 75 miles (120 kilometers) from San Francisco.
“Our city has a broken heart this morning,” said Sacramento Mayor Darrell Steinberg.  “We do not know all the facts, but we know that there were massive losses in a very short period of time.”
Police officers patrolled the area near the shooting point two squares from the Capitol about 2 at dawn when they heard shots and rushed to the point, said Police Chief Leicester Police in Journalists.  They found a large crowd gathered and six dead on the street.
Twelve people who police say were shot and injured were taken to a hospital or hospitals.  The Sacramento Fire Department said four of the seven people evacuated by emergency workers suffered serious injuries.  Authorities said some of the victims were taken to hospitals or taken away.
Authorities located “at least one firearm” at the scene, police said in a statement, and urged witnesses or anyone with shooting records to contact police.
“We are asking for the public’s help to help us identify the suspects,” Leicester said.  Asked if authorities were looking for one or more of the suspects, Leicester told reporters she did not know.
Police said in a statement that investigators knew of a video on social media that appeared to show a quarrel before the shooting, but did not yet know if it was relevant to their investigation.
Kelsey Schar was on the fourth floor of the Citizen Hotel when she said she heard gunshots and saw flashes of darkness.  He went to the window and “saw a guy running and just shooting,” Schar told the Associated Press in an interview.
Her friend Madalyn Woodard said she saw a crowd on the street scattering amid the shootings 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 something resembling napkins to try to stop the bleeding.
Sunday’s violence was the third time in the United States this year that at least six people have been killed in mass shootings, according to a database compiled by the Associated Press, USA Today and Northeastern University.  And it was the second mass shooting in Sacramento in five weeks.
On February 28, a father killed his three daughters, a attendant and himself in a church during a weekly surveillance.  David Mora, 39, was armed with a makeshift semi-automatic weapon, although he was under a restrictive measure prohibiting him from possessing a firearm.
Katie Valenzuela, a council member representing the area where the shooting took place, said she had received phone calls reporting many violent incidents in her 15-month-old district.
Valenzuela cried at a news conference as she told reporters that her last phone call woke her up at 2:30 a.m. Sunday with details of the latest tragedy.
“I’m cracked and angry,” he said.  “Our community deserves better than that.”
Steinberg said the city has worked hard to bring people back to its center since the outbreak of the COVID-19 pandemic and that despite the shootings, the city was safe.
California Gov. Gavin Newsom said in a statement that his government is working closely with law enforcement officials.
“What we know at this point is that there has been another mass attack of victims, leaving families with lost loved ones, many injured and a community in grief,” he said.
The area where Sunday’s shootings took place is full of restaurants and bars.  The nightclubs close at 2 in the morning and it is normal for the streets to be crowded at that time.
Kay Harris, 32, told the AP she was asleep when one of her family members called to say they thought her brother Sergio Harris had been killed.  He said he thought he was in the nightclub of London, which is close to filming.
Harris said he has been to the club a few times and described it as a place for “the younger crowd”.  He spent the morning turning the square waiting for news.
“It’s a very absurd, violent act,” he said.
Pamela Harris, Sergio Harris’s mother, told The Sacramento Bee that the family has not heard from him yet.
“We just want to know what happened to him,” Pamela Harris told the newspaper.  “Knowing nothing is just hard to deal with.”
Barry Atsius, a community activist, said he came to the scene shortly after the shooting.
The first thing I saw were victims. I saw a young girl with a whole bunch of blood on her body, a girl pulling out her glass, a young girl screaming, “They killed my sister.” A mother runs, “Where is my son, has my son been shot? ”  he said.
UC Davis Medical Center received four patients from the downtown shooting, spokeswoman Stephanie Winn said.  He refused to provide their gender or circumstances, referring the media to police.
Ten ambulances and fifty first responders from the Sacramento Fire Department responded to the shooting, according to Capt. Keith Wade.

Correction:

This version corrects that the previous mass shooting in Sacramento took place on February 28 and not last month. This version also corrects that four patients from the shooting, not five, were taken to UC Davis Medical Center.