I would for sure address the situation with the childs parents, but for christs sakes people, its just a phone.. you can get a new one.. the same can't be said for childhood.
When I was a child I made alot of mistakes like that, one time I was backing the lawnmower out and hit my moms car, thank god she didn't flip out like some of you guys would have. Mistakes happen, if a child has his health thats the MOST important thing at the end of the day, not your stupid phone.
Trust me, he/she knows they screwed up if they see the phone break, they are already very sorry and scared.