JOLIET, Ill. (CBS) — A jury on Thursday took less than an hour to convict Christoper Vaughn of fatally shooting his wife and three children in 2007 along an Illinois interstate.

The jury of four women and eight men got the case at 3:30 p.m. Thursday after hearing closing arguments that capped a five-week murder trial. Word that a verdict had been reached came at 4:25 p.m., followed quickly by the reading of the jury’s decision in court.

LISTEN: WBBM Newsradio’s Bob Roberts reports

“This case is not just a murder – it’s an atrocity,” Will County State’s Attorney James Glasgow told reporters after the verdict. “To annihilate your family – I can’t think of a more unspeakable crime. The bedrock foundation of our society is the unconditional love we have for our children, and this crime was the antithesis of that.”

Glasgow noted Vaughn did not have any visible reaction as the verdict was read.

“He was just as emotionless when the police interviewed him and showed him the pictures of his family to him,” he said. “He’s a sociopath, he’s a psychopath, he’s going to get life in prison. And after that, he’ll be on his road to perdition.”

Juror Dan Lachat said the prosecution’s evidence, as a whole, proved overwhelming. He also noted Vaughn’s deadpan appearance in court throughout the trial, but another juror, Bob Trax, said he didn’t necessarily read anything into the defendant’s lack of emotion.

“I’m not even sure all of the characteristics of a psychopath,” Trax said near the Will County Courthouse.

He summed up deliberations this way: “I just felt that collectively we did what needed to be done.”

Vaughn’s sentencing was set for Nov. 26. That is the same date another high-profile Will County defendant, Drew Peterson, will be sentenced. The former Bolingbrook police officer was convicted earlier this month of killing his third wife, Kathleen Savio.

In closing arguments, prosecutors and defense attorneys both said Vaughn wanted to leave his family more than five years ago, but defense attorneys denied the Vaughn killed his wife and children to do so. They blamed his wife for the fatal shootings.

Vaughn, 37, is accused of shooting his wife and three children inside the Oswego family’s SUV in June 2007, after waking them up to tell them he was taking them on a trip to a Springfield water park. All four were shot after Vaughn pulled off of Interstate 55 onto an isolated frontage road near Channahon.

After a month of testimony, jurors heard closing arguments from both sides on Thursday. Prosecutors said Vaughn wanted to leave his family and live in the Canadian wilderness, and plotted to kill them and make it look like his wife was responsible.

But defense attorneys have said his wife, Kimberly, was distraught over a troubled marriage and shot Christopher Vaughn before killing the children and taking her own life.

Prosecutor Michael Fitzgerald said Vaughn’s wife and kids were obstacles in his plan to leave the family and live in the Yukon.

“Christopher Vaughn no longer wanted Kimberly, Abigayle, Cassandra and Blake in his life. They were holding him down, and he had to find a way to get out the life he was in,” Fitzgerald said. “And the way he chose was to murder his wife and kids, and make it look like Kimberly did it.”

In the defense’s closing argument, Assistant Will County Public Defender George Lenard acknowledged Vaughn wanted to leave his family, but said he’s not on trial for that. He said the evidence shows it was Vaughn’s wife, Kimberly, who shot her husband and kids, then killed herself.

He reminded the jurors prosecution witnesses said the shot under her chin could have been self-inflicted.

“That’s reasonable doubt,” he said.

Lenard said Vaughn initially told police he couldn’t remember what happened, only because he felt guilty about cheating on his wife, and believed his infidelity drove her to kill.

But Fitzgerald painted Vaughn as callous, saying he was more concerned that paramedics might ruin his clothes while treating a gunshot wound to his leg.

“He made complaints about his boots being cut up and his jacket being ruined, but has not asked about this children,” Fitzgerald said.

He also reminded jurors that Kimberly’s blood was on Christopher’s coat, and asked jurors how that could happen if Christopher was outside the vehicle when Kimberly shot herself, as he claims.

Prosecutors began presenting their rebuttal argument early Thursday afternoon, and jurors could begin deliberations later in the day.

If Vaughn is convicted, he would face a life sentence, as Illinois has abolished the death penalty.