The California gunman who fatally shot a man at a pre-Super Bowl party opened fire because he mistook the San Francisco 49ers flag outside the victim’s home for a rival gang’s colors, according to a new report.

Daniel Gonzalez, 34, a homeless member of the Playboy Sureno gang, walked up to the revelers Saturday — the day before the big game — and shot Frank Rojas, 24, with a makeshift zip gun during a heated argument, the Fresno Bee reported.

Rojas underwent surgery at Community Regional Medical Center, where he was pronounced dead.

Authorities initially said the shooting stemmed from an argument over the Super Bowl, in which the men were “rooting for different teams,” but now believe that Gonzalez mistook the 49ers flag for a rival gang’s in the dispute.

Neither Rojas nor his friends are associated with gangs, police told the paper.

Gonzalez, who was on probation and living in a nearby homeless encampment at the time of the shooting, tossed his weapon after firing and fled but was later arrested.

He has been booked into Fresno County Jail on murder and weapons charges, according to the Bee.