Prosecutors say 26-year-old Robert Green got into an argument with the teenager that ended with Green beating and kicking the boy until he died.
"It was clear to Mr. Green that after the last kick the victim was 'out,'" the prosecutor said.
Police found the boy's body early Saturday morning after Green allegedly dragged the boy's dead body away from the scene of the beating.
Detectives claim Green twice checked the victim's breathing, but never called 911.
"The first time he was able to determine there was only labored breathing," the prosecutor said. "The last time it was clear there was no breathing."
Neighbors say they didn't know the victim well, other than to say he was from Montana and was visiting his uncle.
"I just can't imagine how his parents feel finding out the day before Mother's Day their kid is dead," said a neighbor named Debbie.
Police say they did have a run in with the boy earlier on Friday. Officers picked him up for being drunk and belligerent. He was released to his uncle on Friday night.
It's unclear what led up to the confrontation, but prosecutors say the streets will be safer if Green is in jail.
Green is being held on $1 million bail for suspicion of second-degree murder. He will be back in court on May 15.