Sacramento police announced on Monday that they arrested a suspect in a shooting that killed six people in the capital of California.

Police said a 26-year-old man was booked on charges of assault with a deadly weapon and being a convict carrying a loaded gun.

Detectives worked overnight to comb the crime scene spread out in the center of the capital of California.

District Attorney Anne Marie Schubert said that the man was not arrested on suspicion of homicide, but suggested investigators were making progress.

SWAT teams have so far raided three homes in connection with the shooting, with at least one handgun recovered.

"The investigation is highly complex, involving many witnesses, videos of numerous types and significant physical evidence. This is an ongoing investigation, and we anticipate more arrests in this case," District Attorney Anne Marie Schubert told the Associated Press.

Authorities had said they were looking for at least two people involved with the shooting. Detectives are still trying to determine the motive.

What do we know about the shooting?

The shooting happened in Sacramento's downtown area near the state capital building in the early hours of Sunday morning as bars were closing and people gathered in the streets.

Police said multiple shooters fired more than 100 rounds.

The victims included three men and three women, Sacramento Police Chief Kathy Lester told reporters.

A vigil was held Monday evening attended by grieving relatives, friends and community members.

"America once again mourns for another community devastated. We must do more than mourn; we must act," said US President Joe Biden on Sunday.