A wife looked on in horror as her 85-year-old husband plunged to his death from a 25ft zip wire.
James McNeil never regained consciousness after the fall at the Bay Shore church camp near Detroit on Thursday. He was pronounced dead in hospital the next day.
Huron County Sheriff Kelly Hanson said a harness malfunction could be to blame for the tragedy and added the pensioner's death appears to be an accident.
The camp employee who was working the zip line is certified and trained, authorities said.
Bay Shore Camp is a Christian camp that offers youth activities as well as adult retreats and events.
A statement on their Facebook page said: "On Thursday, September 24, a tragic accident took place at Bay Shore Camp that resulted in the loss of life of one our guests.
"We are deeply saddened by this turn of events...We ask that you hold all those touched by this tragic loss in your prayers."