Sacramento police believe the mass shooting that killed six and injured a dozen others might have been a gangland gun battle that caught innocent bystanders in the crossfire, according to reports.

Sources told the Los Angeles Times that the California carnage early Sunday appears to have been rival gangs using automatic and semi-automatic weapons, including one group firing while driving by in a car.

One of those arrested for having a gun at the scene was also listed in court documents as a “validated” gang member, the Sacramento Bee said.

Police spokesman Sgt. Zach Eaton confirmed to the local paper that detectives are looking “closely” at the possibility that gangs were involved.

“I can’t confirm that gangs have been involved, but we also can’t rule it out,” Eaton told the Bee.

“That’s a motive question, we’re definitely looking at motive,” he said, cautioning that it might take “a little while” to be certain.

More than 100 shots were fired in the early hours of Sunday, sending people leaving clubs and bars running for their lives.

One of two brothers arrested as suspects, Smiley Martin, 27, was only free because he had been released early from a 10-year prison sentence — despite prosecutors having warned that he posed “a significant, unreasonable risk of safety to the community.”

“Martin’s criminal conduct is violent and lengthy,” a Sacramento prosecutor previously warned. “Martin has committed several felony violations and clearly has little regard for human life and the law.”

Martin — who remains hospitalized with serious injuries from the shooting — has been charged with possessing a machine gun.

He was seen hours before the massacre waving around a gun in a Facebook Live video — alongside Joshua Hoye-Lucchesi, 32, one of the six soon killed, according to footage shared by KPIX 5.

Family members confirmed to the station that Hoye-Lucchesi — who was also known as Jay Cee — was the man in the alarming clip with Martin, whom he also posed with for a Facebook photo last month.

The footage also showed Smiley’s 26-year-old brother Dandrae Martin, the first suspect later arrested for possessing a gun by a prohibited person, a charge his brother also faces.

One local who saw the group filming the social media clip said he was so alarmed, he called 911.

“It looks like to me they were planning to go on some type of OK Corral showdown,” the local, who asked not to be identified for his safety, told KPIX 5.

Police believe Smiley — who remains hospitalized with serious injuries from the shooting — had converted a weapon to fire automatically, leading to the machine gun charge.

“They’re very, very dangerous,” Eaton, the police spokesman, told the Bee about the converted weapons. “They’re configured to shoot a lot of rounds in a very, very short amount of time.”

Daviyonne Dawson, the 31-year-old listed as a “validated” gang member, was also charged with being a prohibited person carrying a gun after being caught with a handgun in the immediate aftermath, police said.

“At this time, Dawson is not charged with crimes directly related to the shootings,” police said. He was later released from Sacramento County Main Jail after posting a $500,000 bail bond, the Bee said.

Dandrae Martin — who said on social media that he was also “hit” by gunfire — wore orange jail scrubs when he appeared in Sacramento Superior Court on Tuesday on a single charge of illegally possessing a weapon.

He did not enter a plea and was held in custody ahead of his next hearing, set for April 26.

“This is obviously very serious,” his pro bono attorney, Linda Parisi, told the LA Times outside court, insisting the suspect’s mood was “very somber.”

So far, no one has been charged with homicide.