EL CAJON, Calif. — A black man reportedly acting erratically at a strip mall in suburban San Diego was shot and killed by police after pulling an object from his pocket, pointing it at officers and assuming a “shooting stance,” authorities said.

One of the officers tried and failed to subdue the unidentified man with a stun gun before the other officer fired several times, El Cajon Police Chief Jeff Davis said at a late night news conference. Davis would not say what the object was, but acknowledged it was not a weapon.

Before police announced the death, dozens of protesters gathered at the shooting scene, with some claiming the man was shot with his hands raised.

Police disputed that and produced a frame from cellphone video taken by a witness that appeared to show the man in the “shooting stance” as two officers approached with weapons drawn.

The fatal shooting comes just weeks after black men were shot and killed by police in Tulsa, Oklahoma, and in Charlotte, North Carolina, where violent protests broke out.

The El Cajon protest was angry but peaceful. Several dozen people, most of them black, gathered and some cursed at officers guarding the scene. They chanted “black lives matter!” and “hands up, don’t shoot!”

Davis urged the community to remain calm and said the investigation will be thorough. “This will be transparent,” he said. “This will be looked at by multiple sets of eyes, and not just ours.”

The District Attorney was on scene and also will investigate.

Police said they were called to the mall shortly after 2 p.m. by the sister of a man in his 30s who said he was “not acting like himself” and walking in traffic.

They say the man refused “multiple” orders to take his hand from his pocket, then was shot after pulling out the object.

When detectives arrived police say a female witness came forward and voluntarily provided cellphone video of the incident. Authorities did not release the video, only the single frame from it. El Cajon officers do not wear body cameras.

Meantime, other videos quickly surfaced showing the aftermath. In one posted to Facebook, an unidentified woman is heard telling police at the scene that the man was ordered to take his hand out of his pocket.

“I said: ‘Take your hand out your pocket, baby, or they’re going to shoot you.’ He said ‘no, no, no,’ ” the woman said. “When he lifted his hand out … he did have something in his hand but it wasn’t no gun, and that’s when they shot him.”

Another woman on the video who was wearing hospital-style work clothing said she’s the man’s sister.

She appeared distraught, repeatedly shrieking and crying, telling officers that she had called them to help her brother, who she described as mentally ill. “I just called for help, and you came and killed him,” she said.

Michael Ray Rodriguez was among the witnesses who said the man had his hands in the air. He said that he was driving out of his apartment complex past the shooting scene and saw a shirtless black man with his hands raised.

The officer “let go of the trigger and shot him again and again,” Rodriguez told the San Diego Union-Tribune.

El Cajon is about 15 miles northeast of San Diego and has a population of about 100,000. It is 69 percent white and 6 percent black, according to 2010 census figures, and has become a home for many refugees fleeing Iraq and, more recently, Syria.