Former Michigan State Police trooper testifies on the stand Thursday in his own defense.
"He looked like a grown man," Mark Bessner said. "(But) he was a boy."
Bessner was the only witness for his defense Thursday.
He's on trial in the death of Damon Grimes, 15, who was riding his ATV in his neighborhood on Detroit's east side on Aug. 26, 2017.
Bessner claims the teen reached for his waistband two times, leading him to think Grimes was reaching for a gun.
The former trooper said he believes he was justified in deploying his taser at Grimes, who then crashed into a parked pickup truck and died from blunt force trauma to his head.
"I thought it was at the time," Bessner testified. "I know now, it was a terrible decision."
It's illegal to ride an ATV on residential streets in Detroit.
Bessner told jurors all they have to do is go to Youtube to see ATV riders in the city are a "huge problem" as they ride 50 to 100 at a time "terrorizing neighborhoods."
That testimony contradicts a Detroit Police officer, assigned to the 9th Precinct, who testified for the prosecution that there are no gangs of ATV riders wreaking havoc in the area.
Grimes was alone on his ATV.
Bessner told jurors that the chase, which only lasted about 45 seconds, began when Grimes came at their patrol car at a high rate of speed.
Bessner said he was in the passenger seat and his partner, Ethan Berger, was driving when they began to pursue the ATV whose rider then slowed down.
During his testimony, Bessner said that he didn't know if the person on the ATV was "taunting" them or trying to "lure" them into a trap.
"I didn't know what to think," said Bessner while also testifying that much of what followed the crash was a blur.
Bessner said he doesn't recall whether he first tried to render aid or check Grimes for a weapon.
He testified that he was shocked when he didn't find a gun, and also stunned when he learned the person he tased was just 15 years old. Then the 44-year-old began to sob on the stand.
"All I could think of was this family lost their son," Bessner said. "And all I could think of was my daughter and what they must be going through. I can't bring Mr. Grimes back and I can't fix my family."
The case resumes Monday morning with closing arguments.