The man fatally shot by California police was unarmed, and reportedly had a mental illness

A woman reported to be the sister of an unarmed black man who was fatally shot by police on Tuesday in El Cajon, California, said in a video from the scene that her brother had a mental illness, and she called police to "help him, not to kill him."

The man has not yet been named by police, but media reports have identified him as 30-year-old Alfred Olango.

Police had first arrived at the scene after receiving calls about a man who was "not acting like himself" and walking through traffic, according to a statement from the police department.

The man had first ignored officers' commands to remove his hands from his pockets, then quickly drew an object from his front pocket and assumed a "shooting stance," police said.

The video, shot on Facebook Live by bystander Rumbie Mubaiwa, shows the woman asking why police had used a gun rather than a Taser to de-escalate the situation. She also says she should have called a "crisis communication team" rather than police.

"Why couldn't you Tase him? I told you he's sick. And you guys shot him," she says in the video, crying. "He's sick, he needs help."

In a statement, the police department said one of the two officers at the scene did indeed use a "less lethal electronic control device" - but it was deployed at the same time the other other officer fired his gun.

Witnesses at the scene also described the man as "mentally challenged" to local media, and one said said he had suffered a seizure before officers fired. Friends of the man's family also told the San Diego Tribune that he had a mental illness.

The incident set off protests in the city Tuesday night, and more have been planned for Wednesday, according to Reuters.

The incident is the latest of several recent police shootings of people with mental illnesses or disabilities that have garnered national attention - last week in Charlotte, North Carolina, police fatally shot Keith Lamont Scott, who's wife said had a traumatic brain injury and "just took his medicine" before the shooting occurred.

A report earlier this year from the Ruderman Family Foundation found that people with disabilities make up a third to half of all people killed by police officers.