The delinquency petition filed in Kent County Circuit Court said the 12-year-old told investigators he's "bad and always does stupid things." He added he thought he'd be killed "for doing something like this," according to The Grand Rapids Press.
The Associated Press couldn't obtain a copy of the document because the court was closed.
A message was left for the boy's attorney, Charles Boekeloo, who entered a not-guilty plea for his client Tuesday, a day after the stabbing of Michael Connor Verkerke in Kentwood, near Grand Rapids.
The 9-year-old ran home and collapsed on the porch after he was repeatedly stabbed at a mobile home park, according to police, and later died at the hospital. Investigators said the older boy left the playground and called police from a nearby home to turn himself in.
The 12-year-old said he didn't know how many times he stabbed Michael Verkerke. He initially said he wasn't concerned for the victim, then said he was concerned because "it made him feel stupid," an investigator wrote.
The AP isn't naming the boy because of his age. He is designated as an adult in the juvenile court system, which would allow the boy, if convicted, to be sentenced as a juvenile and then as an adult once he turns 21.