It took a jury less than three hours to find 29-year-old Keith Lintz guilty of the February 2010 murders of John and Carolyn Tarwacki.
Lintz was convicted on two charges of premeditated first-degree murder and one charge of carrying a firearm to commit a crime.
Police say he shot and stabbed the Tarwackis in their Niles home.
Lintz was arrested for the murdering the Tarwacki's in October of 2012.
The murder charges carry mandatory life without parole sentences.
The verdict came down just after 5 p.m. on Friday after closing arguments from both sides in the morning.
It was an emotional end to the 7-day trial, with families on both sides bursting into tears after hearing the jury's decision. Lintz was noticeably shaken.
"He's stunned," said Lintz's defense attorney Greg Feldman. "He's stunned."
Among the people who testified during the trial were forensic experts who aid there was no DNA evidence to link Lintz to the crime scene.
But, the circumstantial evidence proved to be key after several witnesses testified Lintz talked to them about his involvement in the horrific crime.
"It was a very difficult case," Feldman said. "There was a lot of paperwork involved in it. My files were 5,000 to 6,000 pages deep. Had to come to a conclusion at some point. Didn't go my client's way."
But, the guilty verdict is one Carolyn and John Tarwackis' families have been waiting on for years as the mystery of the horrific crime haunted them.
"You'd always be looking behind your back because you don't know if something else is going to happen in your area," said Carolyn's mother Sharon McKnight. "I just live two doors down with my daughter. And, it's been hard. It's been hard. You had to change your way of living."
The family calls the verdict bittersweet; it won't bring the couple back, but people have some peace now that they know what happened.
"It's a relief in a way," said John Tarwacki Sr. "At least now we know who did it and maybe why they did it, how it all happened. Those questions were still in our mind."
Tarwacki says in the years since he found his son and daughter-in-law brutally murdered, he's never stopped talking to them. And, after more than three years, he finally has some good news to send up.
"I'm going to say, 'We got him, Johnny,'" Tarwacki Sr. said with a smile.
Lintz's case will now go to automatic appeal.
A sentencing hearing is scheduled for Oct. 11.