ITA, tlcox, this behavior doesn't suddenly rear its ugly head one day. A few things that really bother me is that the 15 year old was led into previously unreported behavior. He's either highly impressionable or is extremely immature. Both of those issues, IMO, would rule him out as a babysitter. Can he do CPR, does he know basic first aid, etc.? He obviously did not put the baby's safety first. If he was 8, I'd be yelling for the parents to be locked up. But he's of a legal age to be babysitting and should be tried for his crime the same as any other caregiver.
We'll have to wait and see what comes out in the wash concerning the boys across the street. If they were forbidden in the house, what caused the brother to give in and let them in? I'm very interested in the dynamics here as I think parents need to pay attention to red flags and peer pressure.
Another frightful thought I had is that the three boys might have been watching *advertiser censored* and, given their ages, acted out. Tragic all around.