An altercation inside a Detroit nightclub led to the death of D-12 rapper Proof after an argument allegedly turned into a gunfight, leaving a bouncer wounded, according to sources.

A source that requested anonymity said that Proof was in the club after-hours when a heated verbal argument between Proof and a bouncer allegedly broke out and escalated.

Proof was shot and killed around 4:30 am on April 11 and the bouncer was seriously wounded, both with gunshots to the head.

Police are still releasing details in the shooting and have identified the second man as 35-year-old Keith Bender. Bender is alive, but is still in critical condition.

Sources said that the two men may have pulled guns on each other during the melee, or that a third bouncer had possibly shot Proof as a result of the gunplay.

Police are still trying to piece together details of the shooting but have stated they believe two guns were used in the shooting.

According to sources, Proof was licensed to carry his weapon.

Officers have frequently been called to the club, taking 18 incident reports since 1996.

The club was raided in December of 2005 for selling alcohol to minors and Proof's murder was the third time a shooting had occurred at or near the club.

The police questioned one witness in the case and seek to speak to others to find suspects. The club did not have a video surveillance system police, officers revealed.

Proof who served as Eminem's best man in the rapper's short lived weding to Kim Mathers. The rapper, whose real name is Deshaun Holton, leaves behind a wife and five children.