SOUTH SAN FRANCISCO, Calif.—“I’ve lived here for 50 years and they just killed my nephew,” Dolores Piper said as she protested outside the Arco gas station here where 15-year-old Derrick Gaines was killed by cops June 5.

Derrick and a friend were walking from a McDonald’s when they were stopped by a police officer. When Derrick ran, the cop chased and fatally shot him. Police claim Derrick pulled out a gun. A pistol was recovered, but friends and family don’t believe Derrick threatened the cop’s life.

Supporters of Derrick Gaines have gathered for several days at the Arco station, with signs to protest the killing. Many passersby honk in support. Others have said Derrick got what he deserved.

“I have a 15-year-old son. It could have been him,” said Mona Uli-López, who helped organize the sign making. She and her son have been at the protest every day.

The two youth were stopped because they were “engaging in suspicious behavior,” police spokesman Capt. Mike Brosnan told reporters at a news conference a day after the killing. Brosnan would not comment on whether Derrick pointed a gun at the cop.

Many of the protesters are in their early teens and report an increase in cop harassment of youth since school let out a week ago. They are demanding cops stop racial profiling, which they believe led to the death of their friend.

—WILLIE COTTON