Can a 15 yr old girl be out at 2 am with a 18 yr old boy in Texas?

My son and his friends just turned 18 a few days ago, my sons new girlfriend is 15 yrs old, won't be 16 until sept. She and her girlfriends met my son and his friends without her grandparents permission, the girls all jumped out the window, after the grandparents went to bed..They just all drove around and hung out and the local store parking lot, but didn't get home until 2 am.Can my son get in trouble?