Arlington officer Brad Miller, 49, could also face criminal charges once police complete their investigation, Police Chief Will Johnson said.
Christian Taylor's death came two days before the anniversary of the death of Michael Brown, an unarmed, black 18-year-old who was fatally shot by a white police officer in Ferguson, Missouri.
Brown's death helped spur protests and a nationwide "Black Lives Matter" movement to demand reforms to how police treat minorities.
Instead of setting up a perimeter around the showroom, Miller confronted Taylor and ordered him to get down on the ground, Johnson said. Taylor did not comply. Instead, he began "actively advancing toward Officer Miller," Johnson said.
Miller's field training officer, who had followed Miller into the showroom, drew his own Taser. The training officer heard a single pop of what he thought was Miller's Taser, but Miller actually had drawn his service weapon and fired it at Taylor, who is believed to have been 7 to 10 feet (2.1 to 3 meters) away, Johnson said.
"Decisions were made that had catastrophic outcomes," Johnson said.
The Arlington Municipal Patrolman's Association issued a statement last night decrying Johnson's decision.
An attorney for Miller did not have an immediate comment on Johnson's announcement. Taylor's family did not immediately respond to a request for comment.
Taylor, who was black, was a graduate of an Arlington high school and a football player at Angelo State University in West Texas. Miller is white.
At a protest last night outside the Arlington police headquarters, about 60 demonstrators demanded that Miller be charged with a crime.
Before his final confrontation with Miller, Taylor allegedly held up a set of car keys and told another officer that he intended to steal a car, Johnson said.
