It began as a routine call for a suspicious vehicle. In the chaotic seconds that followed, a police officer riddled a Sunday school teacher’s Jeep Wrangler with bullets, leaving her dead with a gunshot wound to the back of the head.

As the trial of the former Culpeper officer accused of killing 54-year-old Patricia Cook began in earnest Wednesday, prosecutors and a defense attorney offered clashing answers to the question that has gripped this small town since February: How could a simple check end in such violence?

Special prosecutor Jim Fisher said Daniel Harmon-Wright used deadly force when none was needed, that he was not in danger when he opened fire, even after a tussle with Cook.

“At the end of the day, this is a man who shot a woman in the back. . . . There was no threat. It was unjustified, it was excessive, and it was illegal. It was, in fact, murder,” Fisher said in his opening statement in Culpeper Circuit Court.

Daniel L. Hawes, an attorney for the defendant, said Cook’s actions on the morning of Feb. 9, 2012, threatened Harmon-Wright’s life and the public, forcing him to make a split-second decision.

“She was bent on destruction,” Hawes said of Cook. “He stopped her the best way he could.”

Fisher said Harmon-Wright headed to a Catholic school in response to a call about a suspicious vehicle in the parking lot. Harmon-Wright approached the Jeep and asked Cook why she was there, Fisher said, and Cook told him that she was waiting for a friend.

When Harmon-Wright requested Cook’s license, Fisher said, she held it up to the driver’s side window, which was partially rolled down. Harmon-Wright reached for the license, Fisher said, but Cook wouldn’t let go and a “tug of war” ensued.

Cook then cranked up the window, Fisher said, catching Harmon-­Wright’s left hand. The prosecutor said that Cook began slowly driving away and that Harmon-­Wright hopped on the Jeep’s running board, then managed to free his arm and jump off after about 10 feet.

Fisher said Harmon-Wright fell behind the vehicle but then caught up and put his hand on the driver’s side door handle and yelled: “Stop or I’ll shoot! Stop or I’ll shoot!”

Harmon-Wright then fired two shots through the driver’s side window when Cook didn’t comply, striking her in the face and arm. Cook made a left turn onto a public road and kept driving.

When Cook got 20 or 30 feet away, Fisher said, Harmon-Wright fired five shots at the back of her vehicle. One shot went through her headrest, striking her in the head; another severed her spine and struck her heart, Fisher said. Cook died at the scene.

The most dramatic moment Wednesday came as prosecutors showed a video of Harmon-Wright’s interview with an investigator shortly after the killing. It was the first time that the former police officer’s account of events had been made public in his own words.

The narrative was largely similar to the prosecutor’s version, but it differed when delving into the crucial few seconds in which Harmon-­Wright opened fire. He said that Cook had trapped his arm in the window and that he couldn’t get it free.

He said Cook was driving at about 10 to 15 mph, slowed down and then sped up again. He said he feared for his safety, so he fired at the window to free his arm.

“I felt my life was in danger,” Harmon-Wright says in the video.

Harmon-Wright fired the five additional shots in the seconds after getting free. Hawes said Harmon-­Wright fired those shots because a sunscreen in Cook’s windshield was blocking her view and he was worried that she was headed toward a busy area of Culpeper.

At some points in the video, Harmon-Wright appears emotional about taking a life. At others, he expresses worry about his future in the police force.

“My career is done,” he tells the investigator.