PHOENIX - One of the two young boys who were repeatedly bludgeoned by someone who apparently followed them into a playground died early Friday, police said.

Jesse Ramirez, 7, died of the injuries he suffered in the Tuesday attack, police Sgt. Tommy Thompson said. His cousin, 10-year-old Edwin Pellecier, remained in "extremely" critical condition, Thompson said.

Police arrested 36-year-old Joe Sauceda Gallegos within hours of the attack. He was charged Friday with first-degree murder, after appearing in court Wednesday on two counts of child abuse and dangerous crimes against children.

"It was just a brutal, vicious attack that didn't need to happen," Thompson said.

Doctors told police they believe the boys were bludgeoned repeatedly with a baseball bat or similar object. Police say they found a bat in Gallegos' home along with clothing that appeared to be bloodstained.

Thompson said Gallegos, who lived nearby, followed two boys to the small neighborhood park and attacked them, then walked back to his home. Police don't know a motive.

Police said video from a surveillance camera mounted on a house near the park showed the boys walking toward the park, followed a minute later by a man carrying an object that looked like a bat. The occupant of the house said the man looked like his neighbor, Gallegos.

An uncle of Gallegos, Joe Sauceda, told police that he believed Gallegos had been diagnosed as a schizophrenic. The uncle also said Gallegos had told authorities about six months ago that he killed his sons in his attic, but police never found any such victims at the house. Gallegos' sons live with their mother in Colorado and are the same ages of the boys who were attacked.