Police on Wednesday arrested an 18-year-old man charged with stabbing his half brothers, 11-year-old twins, killing one of them and leaving the other seriously injured.

Troy Hill was arrested after he emerged from some woods in Penn Hills, the same Pittsburgh suburb where he is alleged to have stabbed the twins.

Search dogs were unable to locate Hill Tuesday night, but police they arrested him Wednesday afternoon when he walked out of a wooded area beyond the perimeter where police previously searched. Allegheny County Police Assistant Superintendent James Morton said he did not know how far away from the home Hill was found.

"I know it's not where we were looking for him last night," Morton said Wednesday afternoon. "He just continued farther into the woods than we thought he did."

The boys' grandfather found the twins, Tyrel and Tyron, stabbed in the bloody home when he went to check on them after school Tuesday.

Tyron Hill died at the scene while his brother, Tyrel, was taken to Children's Hospital of Pittsburgh, where he was in satisfactory condition and expected to survive.

Allegheny County police charged Troy Hill with one count each of criminal homicide and attempted homicide because they said the surviving twin identified his brother as the attacker.

Police Assistant Superintendent James Morton said authorities believe Troy Hill has emotional problems, but stopped short of offering a motive for the attacks.

"There was blood everywhere," the boys' grandfather, Lovett Williams said. "Everywhere. Blood all over the house. Downstairs, up the steps."

He then heard one of the boys calling out, "Pappy, I'm dead. I'm dying," and found Tyrel Hill hiding in the attic, bleeding and wrapped in a blanket. "I said, 'Who did this?' He said, 'Troy."'

Tyrel's brother, Tyron, was also in the attic, stabbed to death.

Troy Hill played football for Penn Hills High School and played defensive back at Waynesburg College last season, but did not return to college for the fall semester.

The twins played for the Guyasuta Area Football Association in suburban Fox Chapel. Tyrel is a quarterback and Tyron was a running back.

Penn Hills School District officials said grief counselors would be available Wednesday at Linton Middle School to help the boys' classmates cope.

"I don't know how I'm going to make it," Williams said. "I moved here so I could be with my grandsons. I hope I can survive. As long as (Tyrel) makes it, I might make it, too."