Michael Langan had a knife, the ability to use it and was standing dangerously near a Winnipeg officer "trapped" in a police car who was ordering him to drop it.
Const. Michael Temple concluded his partner, Const. Ryan Naismith, was "absolutely justified" in firing his Taser gun to subdue Langan.
The 17-year-old died minutes later.
"At that moment, I was in absolute fear of Ryan's life," Temple on Tuesday told a judicial inquest into Langan's July 22, 2008, death.
"Someone in close proximity, armed with a knife and he's trapped in the cruiser car," Temple said. "If he lunged at Ryan, he was going to be successful (in wounding or killing him)."
Temple and Naismith went searching for Langan after being flagged down by passersby and told he'd broken into a car minutes earlier at a Notre Dame Avenue business. They had no information Langan was armed with a weapon, Temple said.
Temple drove the police cruiser into a William Avenue back lane and saw Langan some distance away, walking toward the vehicle. Langan crossed over the lane when he saw the police, Temple testified. The officers drove up the lane to attempt to catch him.
As he rolled up to the driveway where Langan stood, Temple said he saw Langan aggressively whipping off a heavy jacket he was wearing and "squared up" to face the police car.
He stood about three to five feet away from the open passenger window where Naismith was, Temple estimated.
"I thought he was prepping to fight," said Temple.
The events that unfolded next took mere seconds, the 14-year officer testified. As the car came to a halt, Temple said he looked through the passenger-side window and saw the red laser sight marks from Naismith's Taser gun on Langan's bare chest.
"As I'm putting it in park, (Naismith) says, 'drop the knife, drop the knife,' " Temple said.
"Tase him, tase him, tase him," Temple said he yelled over top of his partner's commands.
He said this while rushing around the back of the police car to cover the suspect with his firearm. Temple said as he reached the rear of the car, Langan was already on the ground, having fallen backwards from the standard five-second Taser discharge.
Naismith kicked a knife from Langan's hand and Temple moved in to handcuff him, he said. He noticed blood around Langan's head and called for an ambulance.
Langan was pronounced dead at Health Sciences Centre not long after.
Naismith is slated to testify today.