SAN DIEGO -- Two young men were behind bars Saturday in the robbery and shooting death of a 17-year-old Southwest High School girl at a South Bay park.

Samson Mendoza, 21, and Basilio Bernard, 22, were arrested at a fast-food restaurant early Friday, about three hours after Donna Hernandez was shot to death, San Diego police Lt. Mike Hurley said.

Hernandez, a senior who had just led a rally and attended a homecoming football game at the school, was in a car with two friends at South Bay Community Park about 9:30 Friday night when two men with bandannas on their faces robbed them of cash and cellular telephones, 10News reported.

It was unclear why the girl was shot.

Hernandez recently moved with her sisters and mother to an apartment about three blocks from the park where she died, according to relatives.

The suspects had been living about a mile away at a housing complex for at- risk youths participating in a federally-sponsored work program, police said.

Detectives searched their rooms and found property stolen during the robbery and a gun believed to be the weapon used to kill the girl, Hurley said.

It was unclear which man pulled the trigger. Both are expected to be charged with murder and robbery.

Family members told the Union-Tribune they plan to set up a bank account for donations to help pay for her funeral.