Babysitter Troubles

We have hired a new 15 year old sitter for our 10 year old son. She is a family friends daughter. 
This past Wednesday she babysat for 3 hours, it was her second time. She and our son had this terrible idea to take our golf cart on a joy ride. Something my son totally knew was off limits. The school where I work, tried calling me as well as the police that never came. 
They drove it thru mud, dangerously sideways down big hills, all thru the greenbelts. They damaged lawns and fences and very much the golf cart. The cart now has cracked fiber glass, seep gauges, cracked wheel well, damaged suspension and steering and who know what else...
Both kids lied about it completely. However the muddy tracks up the driveway, video evidence from local school, tracks everywhere and cart damage are blatant. My kid fit fessed up. But we haven't heard anything from her or her father. 
Now she asks "did you still want me to babysit tonight?"
How would you handle his situation?!?!