Günter Hermann Ewen was born in 1962 in Dillingen, West Germany, as the youngest and only son among five siblings. He suffered from asthma since childhood and showed little interest in school, eventually leaving after the seventh grade. Ewen began consuming alcohol excessively at a young age, influenced by one of his sisters' boyfriends. His early criminal record included theft, fraud, and battery, with multiple arrests for driving under the influence starting in 1982.

In the early 1990s, Ewen's criminal activities escalated to sexual offenses. He was convicted in 1993 for rape and sexual assault in three cases and sentenced to five years and six months in prison. A psychological evaluation described him as a narcissist who pursued his desires without regard for others, especially under the influence of alcohol. He was released in October 1996 after serving two-thirds of his sentence.

After his release, Ewen attempted to start his own business but faced significant setbacks. In August 1998, he was accused by his friend Robert Fisne of multiple burglaries, leading to his arrest. Although he was acquitted in January 1999 due to lack of evidence, the ordeal left him financially and emotionally devastated. He lost his business, home, and girlfriend, and accumulated substantial debt. Ewen then moved in with his sister and brother-in-law in Beckingen, where he lived until the day of the shootings.

On May 16, 1999, Ewen embarked on a deadly rampage that began in his hometown of Dillingen. Around 4:30 a.m., he entered the "Xanadu" discotheque and opened fire, killing the manager, Roland Dekow, and a doorman, and wounding three others. He then proceeded to a nearby apartment, where he killed Robert Fisne—the friend who had previously accused him of burglary—and Fisne's British wife, Shonnette Maxine Fisne. Their 11-year-old daughter, Laura, was also shot but survived.

Ewen fled across the border to Sierck-les-Bains, France. There, he crashed his car and hijacked another vehicle at gunpoint. He broke into a house and murdered a 39-year-old Frenchman, Étienne Kuster. During his escape, he wounded a nurse and a firefighter while attempting to steal another car.

The international manhunt for Ewen ended on May 18, 1999, when police located him in a hotel in Strassen, Luxembourg. As officers stormed his room, Ewen committed suicide by shooting himself in the head.