What would you do if your son came in one night with blood all on his top and down his jeans?

My 19 year old went out last night at about midnight to a birthday party he said, he came back at 3am, I heard him come in, oddly, he put his shirt and jeans straight into the washing machine and went to bed, I got up after he went to bed, paused the wash, and took his shirt and jeans out, his shirt was absolutely covered in blood down the side, almost as if someone had thrown a half pint over him, his jeans were splattered with blood and his shoes had spots of blood. I put the clothes back into the wash and questioned him this morning when he got up, he said there was a fight and somebody was hit with a gl and he helped them up and they were taken to the hospital. He was fine himself, but I'm still a slight bit wary and shocked.. did I do the right thing? I do trust him.