Michael Corbett, who was found guilty in three horrific 1975 homicides, including the rape and murder of actor Kelsey Grammer's sister Karen, has died in Denver.

According to a news release from the Fourth Judicial District DA's office, Corbett, a former soldier based at Fort Carson, perished from natural causes at a metro hospital on Monday, June 24.

The Colorado Springs crime spree that led to Corbett's lengthy imprisonment began on June 19, 1975, when he and Freddie Glenn, a teenage civilian working at the base, fatally shot Four Seasons Hotel cook Daniel Van Lone during a robbery that is said to have netted a mere fifty cents. Just over a week later, the pair killed another Fort Carson soldier, Winfred Proffitt; Corbett reportedly committed the act using a bayonet. Then, on July 1, they tried to rob a Red Lobster restaurant on South Academy Boulevard. The heist was unsuccessful, but they took a hostage — Karen Grammer, who'd been waiting for her boyfriend to get off work. The DA's office says Corbett sexually assaulted her on multiple occasions before taking her to a mobile home park, where Glenn stabbed her to death.

Corbett was convicted in the three murders circa 1976 and sentenced to death — but when Colorado abolished capital punishment two years later, his sentence was changed to life in prison.

The death of Karen Grammer had an enormous impact on John Suthers, the former Colorado Attorney General currently serving as mayor of Colorado Springs, who wrote that the slaying inspired him to become a prosecutor. But it also continued to haunt her brother: "I live with tragedy every day of my life," Kelsey Grammer said during video testimony offered in 2014, when Glenn made an unsuccessful bid for parole. His next opportunity to do so is slated for 2021.

Corbett would have had his own parole hearing in 2020. But final judgment has now been rendered.