DENVER -- Denver police are investigating the shooting death of a prominent medical marijuana advocate over the weekend.

Ken Gorman, 59, was shot to death Saturday night at his home near South Decatur Street and West Mississippi Avenue.

Gorman grew marijuana and sold it for medicinal purposes, but police don't know if theft was a motive in the shooting. Denver police said they do not know if this was a home invasion or if Gorman opened the door for his attackers.

Police do not have anyone in custody.

Police said the shooting occurred sometime after 7 p.m. Gorman was rushed to Denver Health Medical Center, where he died.

Gorman is an activist who promoted passage of Colorado's medical marijuana law in 2000. He helped organize several "smokeouts" at Civic Center Park and on the steps of the state Capitol.

A group of people gathered in front of his home Sunday night and built a small memorial on his front lawn.

Neighbors said Gorman was a quiet, decent man but they did say he had a lot of visitors.