He was one of the members of the Robbery Task Force; a task force filled with members of the FBI, state police, and local cops formed in October 1971 who went rogue and started to take money from the criminals they were supposed to be catching. When they planned to plant the stolen money on Marvin Beckett, he decided to do the right thing and reveal their plan to the FBI, but Robert Kirby killed him with his sniper rifle and framed his death on Marvin Beckett who was locked up for thirty years.
The original autopsy in 1978 stated that Harper was killed when he was shot three times at close range by a .38 Colt Detective Special Revolver. When the Jeffersonian Institution performed another autopsy on his body, they discovered that he was shot in the head by a .38, but the shots to the heart and the left lung were caused by a weapon bigger than the snubnosed revolver.
According to Zack, his ribs and sternum were obliterated by the shots to his chests. The murder weapon was later identified as a military issue M40 A1 sniper rifle with homemade rounds made in the 1970's that were filled with lead pellets. When they went over the list of snipers who were on the task force in the 1970's, Booth discovered that one of the former snipers on the task force was Robert Kirby. Later, they discovered that Kirby was murdered in Brennan's apartment and incinerated the same way and the same place as Delaney.
- More info on the task force can be seen on the page recovered from Harper's journal when they showed the reconstruction to Barbara. It mentions that the task force was called the Robbery Task Force and it was formed in October 1971.
- He graduated at the top half of his class in Quantico.
- He was assigned to the Joint State Federal Bank Robbery Task Force.
- Garret Delaney was Harper's supervisor.
- According to Camille Saroyan, Harper died on June 25, 1978 and was interred on July 2, 1978.