He was the bassist for a Seattle hardcore (or "speedcore" as he called it) outfit called March of Crimes. That band's biggest claim to fame, says Shepherd, was a tape that sold a few copies in Finland. At one point, Shepherd enlisted Stone Gossard to play guitar (Gossard then went on the play in Green River and ultimately wound up in a band called Pearl Jam). Shepherd played in another band called 600 School, and even was a member of Nirvana for a while, though he never played a single note with them.
Shepherd had long been an admirer of a local band called Soundgarden, and even auditioned for them when Hiro Yamamoto quit right before the Louder Than Love tour in 1990. He lost to Jason Everman because he didn't know how to play the songs. When Everman didn't work out, however, Shepherd auditioned again and this time was welcomed into the band he had always idolized, making less money than he had been earning as a carpenter. His first recording session with Soundgarden was the "Room a Thousand Years Wide"/"H.I.V. Baby" single that was released in limited edition on Sub Pop.