San Francisco prosecutors have charged a 19-year-old San Francisco man with one count of murder in connection with a double-fatal shooting at a Mission District pizzeria on Sunday.

The shooting happened at about 4 p.m. Sunday at Papa Potrero’s Pizza at 24th and Potrero streets. Francisco Pena, 41, and Francisco Cornejo, 26, both San Francisco residents, were killed. A third San Francisco man was wounded.

Police believe the shootings stemmed from a conflict between separate factions of the Norteno street gang and may have been retaliation for the shooting of 21-year-old Michael Sanchez, of San Francisco, on Friday night.

Sanchez was killed at 24th and Shotwell streets at about 7:10 p.m. Friday.

Andres Siordia and an unidentified 16-year-old boy were arrested minutes after Sunday’s pizzeria shooting. No one has been arrested for Sanchez’s killing.

Prosecutors have charged Siordia with murder for Pena’s shooting, as well as attempted murder for man who was wounded. However, the district attorney’s office is still considering whether to also charge him for the murder of Cornejo, district attorney’s spokesman Brian Buckelew said in a statement.

That aspect “remains under investigation and a charging decision on that count will be made at a future date,” he said.

Siordia was scheduled to be arraigned on the charges this morning in San Francisco Superior Court.

The 16-year-old boy remains in custody pending a decision on whether to charge him in connection with the shooting, Buckelew said.

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