Stephen Dailey, 21, faces up to 38 years in prison for causing his son's death after he pleaded guilty to child abuse resulting in death in a Denver courtroom on Friday.
Investigators say the abuse happened on Sept. 25, 2009, when Matthew was 8 weeks, 2 days old. He was taken off life-support and died six weeks later.
Dailey was initially charged with first-degree murder, but pleaded guilty as part of a plea deal.
"Investigators said he (Matthew) was shaken and violently thrown against furniture and had gone without oxygen for quite some time. Then my husband at the time called 911," said Valerie Cox, Matthew's mother.
Cox got the call while she was at the grocery store on a quick errand. She'd fed her baby and left him at home sleeping 15 minutes earlier.
"They told me Matthew was not OK and I had to get to the hospital. My heart stopped and I took a deep breath. I threw my cart and ran out of the store," she said. "There isn't a moment that goes by that I don't think about him."
She says she never expected this could happen. She says she and her former husband had planned the pregnancy and were thrilled when their son was born.
"I remember Stephen carried him around everywhere saying, 'This is my baby!' " she said.
Crying is the common trigger for shaken- baby syndrome. The stress of not being able to calm a crying baby can cause some caregivers to become aggressive.
Cox believes other pressures also led to her son's abuse.
"(Dailey) said he was really stressed out. He was going to work. He was going to school full time. He just decided he was just too stressed out and he had to get it out," she said.
Cox is working to get the message out to never shake a baby. She is pleading with anyone who will listen
"Babies can't defend themselves. They are fragile. It is never OK to take out a bad day or a bad moment on them," she said.
"If you are a new dad and you need to go out and go for a walk, don't feel guilty, go do it. If you are a mom and you need a break from your baby, don't feel guilty, go do it. In the meantime, you need to be discussing how you are feeling with someone and reaching out for help."
Lynn Kimbrough, spokesperson for the Denver district attorney's office, said, "Any time you have a parent, in this case a father, who is responsible for their child's death, there is no more tragic a case. It is difficult for the families, for investigators and for the community. It is difficult for everyone involved."
Said Cox: "I just really want people to know that babies are fragile. I want people to know that they can't shake babies. It isn't just shaking a baby; it is brutally beating a baby. I want Matthew to be a prime example of why things must change."