Why the "as an adult"? He's 18, so of course he's facing charges "as an adult." He is one.
You’re right. Legally, 18 is considered an adult crime-wise in Ohio:
http://www.ohio-criminal-lawyer.com/aop/ohio-juvenile-crimes/
But it’s better to call this “juvenille retaliation” so they can imply youth and that the woman deserved it. I reality they “retaliated” against the fact that she called the police after they robbed her.