In addition to the six dead, another 12 people were wounded at the scene near 10th and K streets, police said in a statement.
Officers responding to the sound of shots fired around 2 a.m. found a large group gathered, as well as gunshot victims, the statement said.
Sacramento Police Chief Katherine Lester said the dead included three men and three women. The 12 wounded were being treated at area hospitals, she said in a news conference Sunday afternoon.
She said investigators were interviewing a number of witnesses and located hundreds of pieces of evidence from the scene, including a stolen handgun.
Lester thanked members of the public for sending in tips and video from the incident, some of which she said had also been captured by a nearby police camera.