By Steve Gorman and Daina Beth Solomon

LOS ANGELES (Reuters) - Los Angeles police officers shot and killed a homeless skid-row robbery suspect who grabbed at an officer's gun during a scuffle as they tried to subdue him in a confrontation captured on video, police said on Monday.

The man, known by the street name Africa, had been living for weeks in a tent outside the Union Rescue Mission building where Sunday's shooting occurred and had a history of violent, erratic behavior, the mission's director said.

Footage of the shooting, widely circulated on the Internet, marked the latest in a string of incidents that have put police across the country under heightened scrutiny over the use of lethal force, especially against minorities, the disadvantaged and the mentally ill.

Local civil rights activists called on the city police commission to hold a hearing on the police use of force on skid row, a 50-block area that ranks as one of the largest concentrations of homeless people in United States.

Los Angeles Police Chief Charlie Beck identified the man as a robbery suspect who fought with officers when they tried to take him into custody, then kept resisting as they tried to subdue him with a stun gun.

After falling to the sidewalk, the suspect grabbed at an officer's holstered pistol, precipitating the shooting, Beck told a news conference, adding the weapon appeared to have been partially dislodged.

Bystander video of the incident shows the man swinging his arms wildly at a group of policemen before he is knocked to the pavement, and four officers struggle to restrain him.

Someone in the video is heard repeatedly shouting: "Drop the gun!" and several gunshots ring out, as bystanders gather at the scene shouting at police: "They just shot that man," and "Ain't nobody got no gun."

TENSIONS GROW

Andy Bale, chief executive of the rescue mission, said the shooting immediately increased racial tensions between police and the homeless community on skid row.

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The man shot was black, and police Commander Andrew Smith said one of four officers directly involved in the struggle - the one whose weapon was tampered with - was African-American. The three others opened fire on the man, he said.

Questions about the incident seemed to focus primarily on how police conducted themselves in approaching an individual who may have been mentally ill.

Beck declined to discuss the man's mental history, but the Los Angeles Times reported he had spent time in a mental facility. Bale said the man had previously exhibited a mix of polite cooperation and periodic aggression.

The man had helped workers wash down the sidewalks outside the mission on occasion, but was also involved in at least three other physical altercations in the neighborhood during recent weeks, Bale said.

In one incident, Bale said, the man and a few others dragged a mission worker into an outdoor toilet and "beat him up a bit."

Bale said surveillance footage taken outside the mission showed the man shoving a homeless neighbor about 40 minutes before the shooting, and that this may have been part of what precipitated the robbery report that drew police to the scene.

"There's been some good moments with this gentleman, and some erratic violence," Bale said, adding he believed the man was an African immigrant and that relatives who still lived overseas had "asked him to come home."

Police said an internal investigation had begun. The Los Angeles Police Protective League, an officers union, urged the public to reserve judgment until all facts were known, noting the video suggested the officers believed they "were in life-threatening danger."

(Additional reporting by Chris Michaud and Laila Kearney from New York; Editing by Nick Macfie, Daniel Wallis, Bill Trott, Susan Heavey and)