Christian Taylor, a rising sophomore and defensive back at Angelo State University in San Angelo, was pronounced dead on the scene of the dealership, the department said in an earlier statement obtained by PEOPLE.
Two officers were involved in the arrest attempt, which Johnson said preceded the shooting. Officer Brad Miller fired four rounds, Johnson said, and struck Taylor "multiple" times, though the medical examiner will determine the exact number.
A second officer also discharged his Taser, Johnson said, though it's unclear if it struck Taylor.
Johnson said the investigation has not yet determined the nature of the confrontation between police and Taylor, or the details of their decision-making, but that such information is of "critical importance."
Miller was uninjured and his first interview was still being scheduled as of Saturday, Johnson said. The delay is standard procedure in these cases, he said.
Miller has been placed on leave pending both an administrative and criminal investigation, the department said in its statement. The leave is paid, Johnson said.
The department also said investigators have not yet located footage of the shooting.
Miller, who Johnson said was a trainee near the completion of his field training, was with a field training officer who has 19 years of service.
Miller had no policing history before joining the Arlington department, and no disciplinary or commendation history, the department said.
The FBI has been given the opportunity to participate in the investigation, Johnson said. He said the department would work to be expedient, transparent and thorough.
He has spoken with some members of the Taylor family, he said.
Timeline of events
Taylor was spotted on the property after police were dispatched at about 1:05 a.m. for a possible burglary in progress. The dealership's security company had observed a suspect, who police say was Taylor, on the property.
In surveillance footage obtained by CNN, a man (allegedly Taylor) can be seen apparently smashing through the front gate of the property with an SUV and then stomping on the windshield of a car.
Responding officers surrounded the building "in an attempt to contain and arrest Mr. Taylor for what they believed to be a felony burglary in progress," Johnson said.
They say they made visual and verbal contact with Taylor inside the showroom, after they observed that a dark-colored SUV had been driven through the building's glass doors.
Taylor allegedly ignored their instruction to lie down on the ground and instead fled, Johnson said, and he was attempting to escape through a locked glass door in the southwest part of the building.
Miller and his training officer then approached Taylor inside, to arrest him, Johnson said.
At that point, "there was a confrontation between officers and Mr. Taylor" and he was fatally shot, Johnson said. Investigators will work to determine the exact sequence of actions between the officers.
The initial 911 call, surveillance video recorded by the security company and police radio traffic will be publicly released within seven-10 days, Johnson said, if not sooner.
He acknowledged the community's desire for immediate and concrete facts about the shooting, and that Taylor's death comes during an ongoing national debate about use of force and unequal police treatment.
"The facts available today do not answer all questions, nor will they alleviate all concerns," he said.
Taylor's father said it appears his son may have broken into the dealership. But he could not understand how police decided they had to shoot him.
"What he'd done, ain't no way [that is] right," Adrian Taylor told 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?"
Travis Pride, Taylor’s high school coach, described him to the Dallas Morning News as "a little charmer" and a "fun-loving prankster."
Jayci Korus, a fellow student at Angelo State, told the paper that Taylor's spirit "could touch your heart. Because of him, I'm doing better for me."
Taylor appears to have Tweeted on July 30, "I don't wanna die too younggggg."
I don't wanna die too younggggg— October 13th (@he_got_sneaks) July 31, 2015
"We are still processing this news and are sad for Christian Taylor's family and friends, especially his teammates," ASU said in a statement to PEOPLE.
The football program Tweeted Friday night, "Our thoughts and prayers are with the family of Christian Taylor. Your presence will be missed, but not forgotten. #ramfam."
Our thoughts and prayers are with the family of Christian Taylor. Your presence will be missed, but not forgotten. #ramfam— ASU Ram Football (@ASURamFootball) August 7, 2015
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Additional reporting by DARLA ATLAS