MINERAL POINT, Mo. -- A 75-year-old man who was sentenced to death for killing his wife in a 1992 shooting rampage at the St. Louis County Courthouse has died in prison, the Missouri Department of Corrections said Monday.

Kenneth Baumruk died late Friday at the Potosi Correctional Center in Mineral Point of apparent natural causes, the agency said. He was the oldest inmate on Missouri's death row.

Baumruk pulled two handguns from a briefcase and opened fire in the Clayton courthouse May 5, 1992, killing his wife, Mary, as their divorce hearing was about to begin. He also wounded both of their lawyers, a bailiff and a security guard, and fired at a judge and police officers but missed.

Police returned fire and struck Baumruk nine times, including twice in the head. Authorities said he had carried the .38-caliber handguns in his luggage on a flight from a Seattle, where he was living.

Baumruk initially was ruled incompetent for trial partly because of head injuries suffered when he was shot by police. He was eventually found guilty and sentenced to die in 2001, but the case was thrown out by the Missouri Supreme Court.

A 2007 retrial ended with Baumruk convicted of first-degree murder and again sentenced to die. The jury ignored pleas from Baumruk's lawyers to find him not guilty by reason of what they called a delusional disorder that left him incapable of appreciating the error of his actions.

Baumruk was weeks away from execution in 2009, but the lethal injection was postponed by appeals. The state Supreme Court upheld his conviction in 2012, letting stand lower court rulings that denied his claims of ineffective work by his lawyers.

A new execution date had not been set.