NAPA -- A San Francisco boy trying to help a friend in distress drowned at Lake Berryessa in Napa County over the weekend, authorities said Tuesday.

The Napa County Sheriff's Department has identified the drowning victim as 14-year-old Alan Diaz.

Sheriff's Capt. Jean Donaldson said Diaz was swimming with friends at the beach at Oak Shores on the west side of the lake when a female friend started having trouble swimming.

Diaz went to help her and the girl made it to shore, but Diaz went under the water, Donaldson said.

A man who was in the parking lot heard cries for help and pulled Diaz from the water, Donaldson said.

The spot where Diaz went under is about 10 feet from the shore, where the water is 10-15 feet deep, Donaldson said.

Diaz was taken to the Queen of the Valley Medical Center in Napa where he was pronounced dead around 3 p.m., Donaldson said.