Emotionally UNSTABLE prom date HELP!!!

I'm on the track team with a guy , this guy asked me to prom I said no at first because I had a dreadful feeling but then I said yes and that we could go as friends because I felt badly that no on else would go with him and its just 1 night. JUST FRIENDS that is it. So things were fine I went to track practice everyday said hi and bye was polite to him. Then my best friend tells me that this guy said if I changed my mind again and said that I did not want to go to prom with him that he would snap and either kill himself .. or try to stab people. So we did the smart thing and went to the school social worker and she called him into her office I don't know what she said or asked but I feel like he needs help and I don't feel comfortable going to prom with him. What should I do? My parents don't know about this incident. I want to tell them but I know they'd flip out and call his mother understandably so. But I also I feel like if I DO go to prom with him he might try something crazy AND if I DONT go he'll either kill himself or try to harm someone else and I feel like this should be a way bigger deal then it is but faculty at the school hasn't made it a big deal.