Foster son feeling guilty

My foster son has been feeling guilty. We went down to families house for my cousins funeral. He was nervous and put a not under our door. He was scared to sleep with the other boys. He's 15 and wets the bed. He was also sexually abused by his last foster father and father brothers in a basement and tried to burn the house down because of it. He has so much trauma so instead of sharing a room with the boys. He was gonna sleep on an air mattress in the guest room with us. Everyone treated him nicely. The boys were a bit rowdy but he enjoyed hanging out with them. When it came time for bed the boys were asking why he wasn't sleeping in the room with them. He decided to. I asked was he sure and he said yes. We were gonna have a big breakfast in the morning and I was gonna help finish up last min funeral plans but at like 3 in the morning I hear a bloody murder scream. We on went to the boys room and my foster son was curled in a ball crying. He fell asleep before all the other boys and they saw he was wearing a goodnite pull up so they tried to pull his shorts down to see if he was wearing a diaper and he woke up and thought it was a sexual advance. He wouldn't calm down and me and my husband talked and thought it was best to go home. He said he was sorry and it was okay but we could tell he would have been uncomfortable the whole time. Everyone found out about his bedwetting and he thought these boys were gonna take advantage of him. He keeps apologizing but we keep saying it's fine. The boys parents sent me apologies and said their sons were sorry.

@Briabella those kids were 14-18 and I completely agree! Their parents apologized but said "But it's not like they did it in a sexual way". Regardless of how they meant it teach your kids to keep their hands off people's bodies.