MINNEAPOLIS — A window shatters. The sound of footsteps is followed by sharp cracks of gunshots, a teenager’s groans and a fall. Minutes later, there are more bangs and screams from another teen before she, too, was silenced by a central Minnesota homeowner who was convicted of plotting the whole thing.

A day after Byron Smith was found guilty of premeditated murder, jurors said the audio of the Thanksgiving Day 2012 killings of two unarmed teens — a recording that the 65-year-old switched on before the break-in occurred — was key in his conviction.

“That was the most damning piece of evidence in my mind,” Wes Hatlestad, one of 12 jurors, said Wednesday. “That audio recording of the actual killings and the audio recording of Mr. Smith’s interview immediately after his arrest … pretty much convinced me that we were dealing with a deranged individual.”

Smith shot 17-year-old Nick Brady and 18-year-old Haile Kifer as they descended the stairs into his basement, where prosecutors say Smith was waiting. Prosecutors say Smith had moved his truck to make it look like no one was home, then sat in a chair at the bottom of his stairs with a book, energy bars, a bottle of water and two guns. He also set up a hand-held recorder on a bookshelf.

Defense attorneys said Smith was afraid after prior break-ins and was hiding from intruders, whom he feared were armed. Smith had previously installed video surveillance, and defense attorney Steve Meshbesher said Wednesday that Smith set up the audio recording as another means of protection.

“He was afraid that he might be killed,” Meshbesher said. “He did it in case he was shot and killed in his house, and the police would have some evidence to use, and the family would be able to find the perpetrators.”

Meshbesher said jurors should have heard the whole recording, not just the portion selected by prosecutors. He said Smith plans to appeal.

Ted Sampsell-Jones, a criminal law professor at William Mitchell College of Law, said the audio recording was devastating to the defense, noting that Smith’s taunts to the victims don’t show a man in a panic.

“It was very powerful, and it makes it very clear that … he didn’t do this because he had to. He did it because he wanted to. And that is not what self-defense is about,” Sampsell-Jones said.

The recording captured the sounds of Smith shooting Brady as he came down the stairs. Brady groans after the first and second shots, but is silent after a third shot, and Smith can be heard saying, “You’re dead.”

Prosecutors say Smith put Brady’s body on a tarp and dragged it into another room, then sat down and reloaded his weapon.

Kifer whispers, “Nick?” A shot is fired, and Kifer screams. Smith apologizes as his gun jams, then fires at Kifer four more times and says: “You’re dying.” A sixth and final shot — Smith described it as a “finishing shot” to investigators — was heard soon after.

Hatlestad said he felt early on in the trial that the killings were planned. He said the fact that Smith moved his truck from his home was significant, and he was struck that Smith positioned himself at the bottom of the stairs in “a little hidey hole,” with a tarp ready.

He said jurors went through each charge point by point, “and reasonably quickly came to the conclusion that we thought it was in fact premeditated,” Hatlestad said. He said jurors talked about the “deer stand” that Smith set up to wait for the teens, and he also compared the set up to a “shooting gallery” — a carnival game where a shooter waits for an object to march into view.