It took four days of testimony and more than six hours of deliberations before the verdict. A verdict the family says they've been waiting for, for three long years.
"It was a happy day. It was sad day too, but it's a happy day for our family, because we know we can start healing now, and that's what we want to do," said Rick Chapman, the victims' brother-in-law.
The jury said Gagnon was guilty and the judge said he would spend life in prison for the deaths of Charles and Diane Parker.
Despite that, Gagnon maintained his innocence. He had one final statement before being taken away. "I'm an innocent man, and there is a killer out there mocking us all."
It's a claim friends and family of Charles and Diane Parker just don't believe. They say for the past three years, they've been living in a prison of their own.
"It's been awful, awful, awful. No one knows until this happens to you... no one knows what happens," said Chapman. "It took part of our life when Diane and Charlie left us. It was part of us. Not only was he my brother-in-law, but he was my friend."
Despite years of heartache and days of disturbing testimony surrounding the Parker's murders, friends and family have remained resilient and in the midst of tragedy found strength amongst each other.
"I'm glad it's over with and we can relax and start moving on," said family friend Mike Warren.
Family and friends said while they can start moving on now, they'll never really have closure.
Gagnon's girlfriend, Bambi Bennett, was initially charged in the killings of her mother and step-father too, but prosecutors dropped the charges because of a lack of physical evidence.