Billy Coen

Hey, Queenie! Feast on this!

Billy Coen was a death row inmate that escaped in the Arklay Mountains after the military transport vehicle he was in was forced off the road and was destroyed by a pack of Cerberus. He escaped to the Ecliptic Express where he would later meet S.T.A.R.S. Bravo Team member Rebecca Chambers.

Background
So, you seem to know me. Been fantasizing about me, have you?

Billy was a Second Lieutenant in the United States Marine Corps with Force Recon, who, along with a team of Marines, were sent into hostile territory in Africa to attack a village used as a terrorist training ground. Unfortunately, the air drop was off-target, and as such the team had to march across miles of hostile terrain to their target objective. The heat, combined with enemy attacks, soon reduced the team to four, and when they finally arrived, they found the village was actually full of innocent civilians. In order to cover-up the incident, the squad scapegoats Coen for the ordeal, claiming, "one marine panicked under the extreme conditions and unintentionally killed the civilians." Upon returning to base their base commander, Samuel Regan, had Billy court martialled and sentenced to death. Flashback cutscenes in Resident Evil Zero imply that Billy never took part in the massacres, but he neither confirms nor denies this to Rebecca.

Arklay Mountains Outbreak
Listen, little girl, if you haven't noticed there's some pretty freaked out things on this train. And I, for one, wanna' get out of here. I don't think we stand a chance of doing it alone.

En route to the base for his execution, the military transport vehicle used to take him there was forced off the road by James Marcus, and then Cerberi attacked and mauled the MP's guarding Billy, causing him to run for his life. Billy then sought refuge in the Ecliptic Express, a stranded train, where he met Rebecca Chambers. Despite their radically different backgrounds, the two formed an alliance in order to secure their survival. The two use their talents to pass through many of the obstacles they faced, and discovered the Umbrella Corporation's secrets.

Both were monitored by James Marcus, who sent various creatures to subdue the two. Billy proved his loyalty by saving Chambers several times during the game, whilst Rebecca proved hers by saving him. Coen and Chambers eventually met Marcus. After revealing the details of his mortal demise, the Queen leech residing in his body took control and mutated into the Queen Leech.

The two managed to temporarily subdue the creature, only to discover that a self-destruct protocol had been activated, caused by William Birkin. Matters became even more complicated when the leech returned. In the final battle, Chambers exposed the leech to sunlight, thus making it vulnerable to attack.

Knowing this weakness, Billy acted as bait whilst Rebecca continued to open the roof further until there was no shade left for the creature to hide in. He proceeded to deliver a final shot, which instantly destroyed the leech. In wake of the destruction, Rebecca allowed him to escape, by telling her authorities that he subsequently perished in the Arklay Mountains after their first encounter, keeping his dog-tags as proof. The two bid farewell, and Billy disappeared soon after, not seen again. However, upon returning to Raccoon City, Rebecca filed a report claiming that Billy had died during the initial attack that allowed him to escape, she went on to request a suspension of the case which presumably allowed Billy a chance at freedom.

Trivia

 * When the armored Military Police car transporting Billy crashes due to a pack of Cerberi, he manages to unlock one of his cuffs, effectively allowing him to escape. They dangle from his hand throughout the entire game, in the end Rebecca uses a spare handcuff key to take them off.
 * Billy, Carlos Oliveira and Leon S. Kennedy are the only main characters in the Resident Evil series that have not directly met the series' main antagonist, Albert Wesker, but Leon is aware of him.
 * Like Carlos Oliveira, Billy only appears in two Resident Evil games.
 * Billy has shown he is quite skilled at playing the piano.
 * Billy's tattoo spells "Mother Love".
 * Billy is the only character in the series who cannot mix herbs.
 * Billy has two different official heights, as he is shown in-game to be 5'9, but the Japanese website for Resident Evil 0 lists him as being 5'11. His weight, however, is largely consistent.
 * Billy uses the only piece of profanity in Resident Evil 0- Exclaiming 'shit!' as the Queen Leech finally catches up with the lift he and Rebecca are riding on.