A 13-year old neighbor says he knows the suspect and has even held the baby. He says it all happened around lunchtime Tuesday when the suspect told him the baby fell off a bed and was choking on milk.
"That's what he said, and he like tried to do CPR, but he couldn't, he didn't know how to," said the teen.
The baby was rushed to a hospital and died the next morning. The baby had possible head trauma, according to police. Police began investigating.
"It was suspicious in nature," said Colton Police Detective Ray Mendez. "We had learned the baby had head trauma."
Madrid was arrested later that day. His girlfriend was the child's aunt and the one who had legal custody. Apparently both the mother and father were out of the picture.
As for Madrid, police say he does have a violent past, convicted two years ago of spousal battery.
"It's the worst, it's horrific, these crimes like this are always just horrible, and extremely unfortunate for everyone involved," said Mendez.
If anyone has any information regarding this investigation they are encouraged to call the Colton Police Department at (909) 370-5021 and ask for Detective Robert Wilson.