It is no exaggeration to say that without the rapper Proof, who was fatally shot outside a Detroit nightclub early Tuesday at the age of 32, the world would probably never have heard of Eminem, his friend and frequent collaborator.

The pair met as teenagers and Proof (real name: Deshaun Holton) encouraged the young Marshall Mathers in his attempts to find a distinctive hip-hop voice. Later, it was Proof who formed the Eminem-featuring rap collective D12. After achieving solo fame, Eminem would return the favor, rejoining the sextet for two albums (2001’s Devil’s Night and 2004’s D12 World), and ensuring that Proof was cast alongside him in the autobiographical 2002 film 8 Mile (although the part based on Proof himself would be played by Mekhi Phifer). The pair remained close, and in January, Proof served as Eminem’s best man when he remarried his former wife Kim.

But Proof was far more than just Eminem’s “right-hand man.” He was a talented rapper in his own right whose interests ranged wide as the title of his 2005 solo album Searching For Jerry Garcia amply demonstrated. When I interviewed Proof in 2004 on his home turf of Detroit’s less than salubrious 9 Mile area, he was genuinely delighted when I gave him a Janis Joplin DVD, a present prompted by the fact that he had recorded a track named in honor of the late blues belter.

While admitting some familiarity with the local criminal system — “You don’t know what jails in Michigan are like,” he declared at one point — the polite, soft-spoken man who the rest of D12 referred to as their “big brother” seemed an unlikely candidate that day to become one of hip-hop’s many prematurely deceased. Indeed, he spoke mostly of the concept of giving back to his community — although, Proof admitted with a grateful laugh, he accomplished that in part by looking after a mulberry bush at his grandmother’s house with fingers that had become green from counting his money.

Proof’s shooting (which took place in the hardscrabble 8 Mile neighborhood depicted in the film of the same name) is the latest of several violent incidents involving associates of Eminem. In 1999, D12 member Bugz was murdered. Last New Year’s Eve, Obie Trice was shot, although not fatally. This latest tragedy also eerily echoes the video for Eminem’s 2005 anti-violence anthem Like Toy Soldiers, in which Proof was pictured being killed in a shooting.