City of Chino spokeswoman Michelle Van Der Linden says a man hit the student in the head Thursday afternoon across from Chino High School. The boy was flown to a hospital where he's in critical condition.
The suspect fled after the attack, and the high school and a nearby elementary school were locked down until he was caught soon after.
Van Der Linden says 48-year-old Gregory Richmond was arrested and booked on suspicion of attempted murder.
It wasn't clear whether the man and boy knew each other, or what motivated the attack.
Police didn't know if Richmond had hired an attorney, and no home phone listings could be found.
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