Nevada man Duane Davis has been indicted for the 1996 murder of Tupac Shakur.
Las Vegas police arrested the 60-year-old on Friday morning.
Mr Davis, 60, was the “on-ground, on-site commander” who “ordered the death” of the legendary hip-hop star, according to Chief Deputy District Attorney Marc DiGiacomo.
The rapper’s stepbrother Mopreme Shakur told CNN this moment is “bittersweet.”
“We have been through decades of pain. They have known about this guy, who been running his mouth, for years,” he said.
“So why now?” he added. “For us, this is not over. We want to know why, and if there were any accomplices.”
In July, the Vegas police raided a home connected to the man in the nearby city of Henderson as part of their ongoing investigation.
Shakur was shot in a drive-by shooting in Vegas on 7 September, 1996.