Do you think he is gay?

My friend was sleeping with me. He was in prone position. He moved a little so that his throbbing penis is felt on my thigh. Then he flexed his knee so that it was in air and repeated it twice. Two days ago he was very close to me and his back was facing my back and his butt touching on my butt and he was moving which i felt like he was masturbating. I could see some stain on his trousers next morning which may be semen. I am not sure. I am confused since he has not come out to me or has not touched me or so. So i cannot confront him also. Please tell whether he is gay or is it an erotic dream. I want to know it rightly so that i can do something. Please help.