Thanks to Elaine Mittleman, a former resident of Indiana and a thoughtful federal criminal defense lawyer and appellate specialist, here is an article and video that was completed 25 years after the USPO was killed. In brief, this is what happened:
On September 22, 1986, United States Probation Officer Thomas E. Gahl was killed in the line of duty in Indianapolis, Indiana. It was a Monday morning, not unlike any other Monday morning Tom had experienced in his previous 11 years as a probation officer. That morning, Tom was visiting the home of parolee Michael Wayne Jackson. Tom arrived at the home at approximately 8:15. After not being able to contact Jackson, Tom turned to leave the residence, but Jackson ambushed Tom and shot him three times with a sawed off shotgun. An 11 day manhunt ensued, ending with Jackson taking his own life in Wright City, Missouri.