A 13-year-old boy killed another teen by hitting him in the head with a baseball bat during an argument after a youth game, authorities said Wednesday.

Jeremy Rourke (search), 15, was pronounced dead at a hospital after the Tuesday night attack, said Brenda Shafer, a spokeswoman for the coroner's office.

A homicide investigation was under way, but the younger boy had not been arrested, said Don Manumaleuna, a sheriff's spokesman. Authorities said the boy was detained after the incident.

"He just didn't realize it, it just happened and before you know it. ... I told him, 'What did you do, why did you do that?"' parent Sam Cordova told Fox 11 News.

"I could see it in his eyes that it was starting to sink in, oh my gosh, what did I do?"

The nature of the argument at a concession stand was unclear. Authorities did not know whether the boys were spectators or members of the baseball teams that had played.

The Pony League field in Palmdale, about 40 miles northeast of Los Angeles, has a sign promoting sign-ups for boys 5 to 14 and encouraging parents to "Protect Our Nation's Youth." (search)