Who witnessed Tupac Shakur’s 1996 killing in Las Vegas? Here’s what we know.

 Who witnessed Tupac Shakur’s 1996 killing in Las Vegas? Here’s what we know.

Duane “Keffe D” Davis is the last living suspect in one of hip-hop’s most enduring mysteries — the 1996 death of rapper Tupac Shakur in Las Vegas.

Police and prosecutors say the shooting stemmed from a fierce competition for dominance in a musical genre that pitted East Coast members of a Bloods gang sect against West Coast members of a Crips s…