Murder charges have been filed against two San Francisco boys for their alleged roles in a daytime melee inside a Mission District pizzeria in September that left two men dead.

The victims, Francisco Pena, 41, and Francisco Cornejo, 26, were shot to death the afternoon of Sept. 20 inside Papa Potrero’s Pizza at 24th and Potrero streets.

Investigators believe the shootings may be linked to the killing of another man two days earlier, and that the violence stemmed from a dispute between rival factions of the Norteno street gang.

Video footage from the pizzeria shows that the shooting was preceded by a brawl between several people wielding barstools, according to prosecutors.

Andres Siordia, 19, of San Francisco, was arrested minutes after the killing and was charged with Pena’s murder and the attempted murder of a third man who was wounded inside the restaurant.

Siordia has pleaded not guilty to the charges and is due back in court on Friday. His attorney has claimed Siordia had been trying to defend his friends from the shooting victims.

Last month, two boys, ages 17 and 15, were charged in juvenile court, district attorney’s office spokesman Brian Buckelew said today. Their names have not been released.

The 17-year-old was also arrested the day of the pizzeria killings, and the 15-year-old was taken into custody in December, Buckelew said.

Both have been charged with Pena’s murder and assault with a deadly weapon for allegedly attacking Pena with barstools and glass plates, Buckelew said. The 17-year-old also faces attempted murder and assault charges for the third victim.

They were arraigned on the charges Dec. 18.

Prosecutors have not yet charged anyone with Cornejo’s killing.

“We’re close to making a charging decision about that,” Buckelew said today.

The shooting believed to have sparked the Papa Potrero’s violence occurred on Sept. 18.

Prosecutors say Siordia was riding in a limousine with a group of men that night when they began arguing with a second group of men at 24th and Shotwell streets.

One of the men in the limo, Michael Sanchez, 21, of San Francisco, was shot and killed.

If convicted of the charges stemming from the Papa Potrero’s shootings, Siordia could face life in prison. The juveniles would be held in a state juvenile prison facility until age 25.

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