Buz Koelbel, who led his father’s Denver-area real estate firm for nearly 40 years before stepping down from the top job earlier this year, has died. Koelbel, 72, died Thursday from blood cancer, according to his family. Buz Koelbel (Provided by Koelbel and Co.) Koelbel’s father, Walter A. Koelbel Sr., was a Michigan native who moved to Colorado for military training in World War II, then stayed to attend the University of Colorado Boulder.