Hexum died after shooting himself in the head with a prop gun loaded with blanks on the set of the CBS series Cover Up, a program about a pair of fashion photographers/models who were actually secret agents. Hexum, who played a weapons expert, was said to constantly be playing with the guns as if they were toys and once angered Jennifer O'Neill so much that she chastised him on-set for his carelessness.[6]
On October 12, 1984, after finishing a scene in which he fired several blank rounds from a .44 Magnum revolver, Hexum's character was supposed to unload the gun and reload it with inert dummy rounds, which was required for the next scene in the script—a procedure that Jon-Erik was not familiar with, and which was usually done by the prop masters. The shooting of the next scene was delayed several times. While waiting for the prop masters to unload the blanks from the gun, Hexum jokingly put the gun up to his temple and allegedly said,
"Let's see if I get myself with this one."
Hexum apparently did not realize that blanks use paper or plastic wadding to seal gun powder into the shell, and that this wadding is propelled out of the barrel of the gun with enough force to cause severe injury or death if the weapon is fired within a few inches of the body, especially if pointed at a particularly vulnerable spot, such as the temple or the eye. Although the paper wadding in the blank that Hexum discharged did not penetrate his skull,[7] the wad struck him in the temple with enough blunt force trauma to shatter a quarter-sized piece of his skull and propel the pieces into his brain.
According to a crew member on the set:
"Jon smiled and pulled the trigger. There was a loud bang and a bright flash, then black smoke. Jon screamed in agony, then looked kind of amazed as he slumped back onto the bed with blood streaming from a severe head wound. It was horrible."
Hexum's assistant ran to him and wrapped his head in a towel. An ambulance was called, but before it could arrive, Hexum slipped into a coma, prompting crew members to carry him to one of the studio's station wagons and drive him to Beverly Hills Medical Center. Hexum went into surgery as his family and girlfriend, actress Elizabeth Daily, were notified of his condition. Initially he was listed as being in "serious" condition, but after five hours of surgery, doctors changed the condition to "critical". Hexum was intubated and connected to a respirator, and lingered for six days before doctors pronounced him brain dead. With his mother's permission, Hexum was flown to San Francisco and taken off life support so that his organs could be donated.[8]
Hexum's death from on-set firearms negligence with blank rounds occurred in similar circumstances to that of another famous actor, Brandon Lee, in 1993. In Lee's case, however, the fatal discharge occurred as a result of prop team negligence (firing a dummy round with an intact primer, causing a squib load, and then unintentionally firing the stuck bullet out of the barrel with a blank round), instead of negligence by the actor.
The same month that Hexum died, an issue of Playgirl magazine came out, featuring a photo shoot that Hexum had done shortly before his demise.
In 1999, Jennifer O'Neill was interviewed for the show Mysteries and Scandals, where she criticized the bad management at the set of Cover Up, which required the actors to stay at the set up to 18 hours a day. She described Hexum as overworked and tired at the time of his accident.
