(Capcom's primary storyline)
"Hey, Queenie! Feast on this!"
Billy Coen was a U.S. Marine Corps Second Lieutenant-turned death-row inmate that escaped into the Arklay Mountains after the military transport vehicle escorting him was forced off the road by a pack of Cerberus. He took refuge in the nearby Ecliptic Express where he would later meet Rebecca Chambers, who had arrived with S.T.A.R.S. to investigate reports of murders in the vicinity.
"So, you seem to know me. Been fantasizing about me, have you?"
In mid-1997, 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 suspected of being used as a guerilla 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.
Billy's commanding officer ordered the execution of the innocent villagers and framed Billy for it, 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-martialed. Under Clause 1; Article 118 of the Uniform Code of Military Justice, Billy was found guilty of 23 counts of first-degree murder. Under military jurisdiction, Billy was eligible for capital punishment and sentenced to death.[excerpt 1]
"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."
Traveling through the Arklay Forest en route to Regathon Base, which was to serve as Billy's place of execution, the military vehicle transporting him was forced off the road by James Marcus. Subsequently, a pack of cerberuses slaughtered the Military Police who was ensuring their prisoner's transport, inevitably forcing him to run for his life. Seeking refuge from his bloodthirsty assailants, Billy took cover inside the Ecliptic Express, where he would eventually cross paths with Rebecca Chambers. Although Rebecca had been ordered by her S.T.A.R.S. superiors to execute Billy on sight as a result of allegations that he had murdered the MPs, Billy persuaded her to cooperate with him in their effort to survive. The two used their skills and situational awareness to navigate the many obstacles that they would face, eventually discovering the Umbrella Corporation's secrets.
Both were monitored by James Marcus, who sent various creatures to subdue them. 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 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, Billy fended off the Queen Leech while Rebecca opened the roof and 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 with a powerful Magnum revolver, which instantly destroyed the leech. They escaped the crumbling facility shortly thereafter. In the 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 as Rebecca heads to meet her comrades while Billy escaped and was never to be seen again.
Upon returning to Raccoon City after the Mansion Incident, Rebecca filed a report falsely claiming that Billy had died during the initial attack on the van, keeping her word.[excerpt 2] According to the report, Bravo Team was forced to leave Billy's body behind at the site of the MP vehicle. She went on to request a suspension of the case. As of September 1998, when the Raccoon City Outbreak occurs, it is unknown if this suspension was carried out. However, any police records of the case are presumed destroyed following Raccoon City's destruction.
Billy Coen's current whereabouts are unknown.
- ↑ Excerpt from biohazard 0 KAITAISHINSHO, page 008:
"23人もの人間を殺害した嫌疑により軍法会議で死刑判決を受けた、 海兵隊の元少尉。刑執行のために護送される途中、通り道であるラクーンフォレストにて逃亡。そばにMPふたりの惨殺体が転がっていたことから、 彼らを殺して脱走した疑いを持たれ、 ブラヴォーチームに追われる身となった。無口で凄みのある男だが、 「第一級殺人犯」という肩書きから想像できるような残虐さは感じさせない。列車内にてレベッカと出会い、 彼女の危機を救ったのをきっかけに、 行動をともにすることになる。"
- ↑ Excerpt from biohazard 0 KAITAISHINSHO, page 245:
- ↑ 1.0 1.1 Capcom. Resident Evil: The Umbrella Chronicles. (Capcom). File: Court Order for Transportation.
- ↑ 2.0 2.1 2.2 2.3 biohazard 0**キャラクター紹介**. Capcom.
- ↑ Voices of Billy Coen, Behind the Voice Actors
- ↑ Capcom. Resident Evil: The Umbrella Chronicles. (Capcom). File: Memo about Billy's Past.
- ↑ biohazard 0 KAITAISHINSHO. Enterbrain. p. 008.
- ↑ Resident Evil Zero, Second Wesker cutscene
- ↑ (in Japanese) biohazard 0 KAITAISHINSHO. Enterbrain. p. 235.
- ↑ Resident Evil 2 (N64), Rebecca's Report