Officers told ABC4 Utah, 30-year-old Joshua Harding is the only suspect wanted in the killing his girlfriend's son Paxton.
"Finally," said Linda Brown.
Brown is Paxton's grandmother. She told ABC4 Utah that after what feels like an eternity, "it's one small step, but a very big step. The wheels of justice are finally moving."
Police arrested Harding on Wednesday. Officers said he was the only person at home with Paxton in November last year when the infant was severely injured. One of those injuries resulted in Paxton's death.
"The child died from trauma to the head," said Lieutenant Mathew Siufanua with the Provo Police Department.
Despite court documents that say Harding had an abusive past and a short temper with Paxton, the arrest took 11 months.
"When it comes to abuse there's so much to look at," said Siufanua. "The whole focus has been putting all of our ducks in a row and making sure we had all the facts right in this case."
Linda Brown said she is grateful for the department's efforts.
"I appreciate their thoroughness to make sure that when it does go to court that it moves forward," she said.
Brown told ABC4 Utah she has slowly come to terms with what happened to her grandson.
"I'm sick. I'm sick that we trusted an individual in our lives that had us all fooled," she said.
However, she plans to make sure justice is served.
"He's not going to get away with this," she said. "You took my three-month-old grandson, took away his voice. I'll be his voice."
Harding will make an initial appearance in court later this month.