The shooting happened around 2:00 a.m. near 10th St and J St, a few blocks from the State Capitol Park. Police said they are searching for the shooter or shooters who opened fire.
Video posted on Twitter showed people running through the street as the sound of rapid gunfire could be heard in the background. Multiple ambulances had been sent to the scene, according to witnesses.
Officials investigating said victims of the shooting were in their 20s and 30s.
Police in Sacramento say six people are dead and at least nine others have been injured after a shooting in downtown.
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 Street.
Harris said she has been to the club a few times and described it as a place for "the younger crowd."
Downtown Sacramento after police reported six had been killed and multiple injured.
"Words can't express my shock & sadness this morning," said Sacramento Mayor Steinberg. "The numbers of dead and wounded are difficult to comprehend."
The mayor added that rising gun violence is "the scourge of our city, state, and nation."
Police said video is circulating on social media that appears to show a fight preceding the shooting. They asked anyone in the community with related video to contact Sacramento police.
Associated Press contributed to this report.