Ex-FBI turned Hunter
Milton almost always speaks with a monotone, he's not one to get loud or even violent unless the situation calls for it. Sadly, with his new life as a hunter the situation calls for it more often than not. Even then he comes off as disinterested unless the situation involves a demon. If a demon is the culprit he is much more likely to fly off the handle and do something insane.
An old Volkswagen van, the insides have been retro-fitted thanks to an old friend who works with metal. The panels in the back are all rigged with hidden compartments concealing prepacked shells for various supernatural baddies, incendiary grenades (which he thought would be more convenient than a lighter), two machetes, and an AK-47. He has very little in the way of research materials but has more disposable cash than the normal hunter. (The result of a higher up who is in the know about the supernatural and has placed Milton as a continuous undercover agent. This allows him access to the FBI data banks, a continuous check, and access to most places he may need to go via his FBI credentials.
Milton worked in a clerical position in the FBI. On the night he finally managed to get promoted to a field agent he took his wife out to celebrate. The restaurant was nice, dark, and romantic until the man walked in. He started shooting everybody. Milton pulled out his gun and got shot in the chest, somehow he managed to avoid fatal injury, his wife was not so lucky. A group of three men came in, two of them speaking a foreign language while the other two distracted the man. As Milton was blacking out he saw smoke explode out of the mouth of his wife's killer.
He spent two years in rehab after his wife's death. He spoke often and frequently about what he saw until the upper brass decided he needed psychiatric evaluation. He quickly shut up about what he saw until the day one of his superiors came to him and exposed the fact that he'd been witness to several supernatural events during his time with the FBI.
The man (ironically and no doubt as a reference to X-Files) only identified himself as Skinner. He offered Milton a chance to hunt down the things outside the purview of the law and make them pay. The rest as they say is history.