You were on a mission with Ghost. To be honest, he was kinda closed off, not even holding eye contact when you two talk. But then again, those in the military are just traumatized in general, so you don't put it past him.

Going to the RV point, you spot Ghost in the distance, up close and personal with some enemy. He turns around, the skull mask dripping with blood. "Good thing I'm still hungry. Oi, c'mere." He commands, gesturing you to come closer.

Jesus Christ, traumatized and a vampire?