By Alex Dobuzinskis
LOS ANGELES (Reuters) - The Los Angeles County Sheriff's Department acknowledged on Tuesday its deputies were mistaken in last month's shooting death of an unarmed black man they encountered lying motionless on the ground and erroneously assumed was a carjacking suspect.
Relatives of the 27-year-old victim, Donnell Thompson Jr., whom they described as suffering from a learning disability, plan to bring a civil rights lawsuit against the county over the July 28 predawn incident, said their attorney, Brian Dunn.
The deputy who fired the fatal shots has been placed on leave, but an investigation into whether the shooting was justified under the circumstances is ongoing, the sheriff's department said in a statement.
The incident caps a growing series of high-profile deaths of unarmed black individuals by police in cities across the country that have reignited a debate over the use of lethal force by police officers and the role of racial bias in the U.S. criminal justice system.
Thompson was shot to death in Compton, a working-class town bordering the city of Los Angeles, as sheriff's deputies were searching for a carjacking suspect who had opened fire on officers.
Deputies discovered Thompson inexplicably lying in the front yard of a home, but he was unresponsive when they sought to gain his attention, according to the latest official account of the incident.
"We don't know why he was in the state he was in," sheriff's Captain Steve Katz said in a telephone interview.
The encounter grew confrontational when a deputy approached Thompson and spotted what was thought to be a weapon nearby, Katz said.
Believing Thompson to be the carjacking suspect, deputies closed in on him using armored vehicles, positioning one on either side of him, then lobbed a concussion grenade in his direction and fired a rubber baton at him.
At that point, Katz said, Thompson rose from the ground and charged toward one of the armored cars with his hand around his waistband, and a deputy in the turret of the vehicle shot him twice with a rifle, Katz said.
Thompson was found to have been unarmed, and subsequent DNA and fingerprint testing showed no tie between him and the carjacking, the department said. The actual suspect was arrested a short time earlier.
But Dunn called the deputies' handling of their encounter with Thompson "a complete tactical blunder on every level."
"It quite possibly generated in his mind a belief that he was going to be harmed," he added.
(Reporting by Alex Dobuzinskis; editing by Steve Gorman and G Crosse)