He was one of the founding members of My Darling Murder, a metal band formed with friends Andy Gerold and Elias Mallin.

Kelleher attended Chaparral High School in Scottsdale, Arizona, and honed in on his craft while writing music and playing in numerous rock and industrial bands.

His influences as a bassist include Billy Gould, Cliff Burton, Rex Brown, and Paul D'Amour.

Kelleher founded My Darling Murder in 2004 with guitarist Andy Gerold, drummer Elias Mallin, and singer Chris Ruoff.

Kelleher was involved in cooperation with Thirty Seconds to Mars since former bassist Matt Wachter left the band in 2007 to join Angels & Airwaves whose schedule was less hectic, allowing him more time for his family.