The officer involved was in the last stages of his field training when he shot Christian Taylor, 19, multiple times at a car dealership in Arlington, Police Chief Will Johnson said.
Footage released by a security company after the incident shows a man described as Taylor wandering around the dealership lot.
In the video, which has been edited, he kicks out the windshield of a car on the lot. Officers are shown walking onto the dealership's parking lot a few moments later.
A security company called 911 about 1 a.m. Friday after Taylor allegedly drove his SUV through the front window of the dealership showroom, Johnson said.
The company monitored Taylor on surveillance cameras and reported a possible burglary in progress.
When officers arrived, Taylor was inside. They yelled at him from the other side of the glass to get on the ground but he ran away and tried to open a locked glass door, Johnson said.
Brad Miller, 49, and his training officer, a 19-year veteran, went inside to arrest Taylor. There was a confrontation in which Miller fired four times and the other officer used a Taser, the chief said.
The sequence of events and gunshots is unclear. Miller was not injured and has not been interviewed, but it is standard procedure to wait a few days before questioning an officer involved in a deadly shooting, the chief said.
Miller, who graduated from the police academy in March, is on routine administrative leave as authorities investigate the shooting. The officer was nearing the end of 16 weeks of field training, Johnson said.
Arlington police officials have invited the FBI to participate in the investigation and review the police department's own investigation and findings.
"The facts available today do not answer all questions or alleviate all concerns," Johnson said.
Surveillance video, police radio traffic and 911 calls will be released in about 10 days after all officers involved have talked to investigators, the chief said.
Taylor was black and Miller is white.
The deadly shooting came almost one year to the day after the death of Michael Brown in Ferguson, Missouri, led to protests nationwide and discussions about race and police shootings.
Father speaks out
Taylor played defensive back at Angelo State University
. Last year's roster listed him as a 5-foot-9, 180-pound freshman.
His father said while it appears his son did wrong, he shouldn't have had to die.
"What he'd done, ain't no way right," Adrian Taylor told CNN affiliate KTVT.
"But to shoot an unarmed man? You're a police officer, you're trained to take down men with your hands. You have your Tasers, you have your clubs, whatever there is. Unarmed, a 19-year-old -- and you shoot to kill?"
Christian Taylor had "no real problems," his father said. He said he often gave a helping hand to the homeless.
"A good dude, man," the father told the station. "We'd be going over here to church and he'd pull over and give a homeless guy money, shoes if he needed and he'd have to go back home and get some more shoes because he gave his away. He was like that."
The father didn't know what could have prompted his son to allegedly drive his SUV into the dealership.
"You know, it could have been too much drinking, he could have been wrong place at the wrong time, he could have gotten something and he didn't know what he was getting," the father told the affiliate.
No body cam, no shooting video
Miller wasn't wearing a body camera because the department doesn't use them, police said. The police department "is in the process of implementing a pilot program for body worn camera use," authorities said in a statement.
He had no previous police experience prior to joining the Arlington force in September 2014. He has been in field training and working under the supervision of a police training officer since graduating from the academy, authorities said.
He has no disciplinary history or commendations, the department said.