In 1978, just weeks after graduating high school, Dahmer picked up hitchhiker Steven Hicks and invited him to his family home for “a few beers”.
They drank together for hours before Hicks asked to leave, at which point Dahmer bludgeoned him twice with a dumbbell before strangling him to death.
The next day he dissected Hicks’ corpse and buried the remains in his yard, only to dig them up later so he could dispose of them more thoroughly.
It’s hard to believe that just a few months after the grizzly murder, Dahmer was allowed to enlist in the US Army and train as a medical specialist.
WATCH: Jeffrey Dahmer discusses his killings
He joined up in January 1979 and underwent basic training in Alabama before beginning his medical training, later serving as a combat medic in West Germany in July that year.
Considered an “average or slightly above average soldier”, his alcoholism soon became a problem and a fellow soldier accused him of sexual assault.
Preston Davis claimed Dahmer assaulted him while they were in the field together and later told TheWrap of Dahmer: "He was a very racist individual, and once he started drinking, he became a very obnoxious individual.”
He also said that Dahmer would drunkenly brag about having killed a man in Ohio.
Another soldier named Billy Capshaw shared a room with Dahmer during their military service and claimed he was sexually assaulted, tortured, and controlled by his roommate.
"It was Dr. Jekyll and Mr. Hyde. I was in a room I was scared to come out of,” he told TheWrap.
“I would steal Jeff's money, thinking that if he didn't have any money, he wouldn't drink anymore and, therefore, wouldn't hurt me anymore. He beat me so badly for that, and to stop me from screaming; he hit me harder."
Though Capshaw claims to have told higher ups of the abuse, his allegations were not taken seriously.
WATCH: Dahmer family's home video footage
“Jeff Dahmer was a sociopath, a psychopath, a narcissist – he was insane,” he said.
However, it was Dahmer’s drinking problem that would see him kicked out of the military in 1981, after a sharp decline in his performance.
He received an honourable discharge, as his superiors noted that Dahmer’s problems during his military service were unlikely to be applicable to civilian life.
After leaving the army, Dahmer would go on to kill 16 more people.