"What happened this weekend with the death of former Navy Seal sniper Chris Kyle at a gun range is exactly the opposite of the evidence-based approach to treating PTSD," termed 'prolonged exposure' or 'virtual reality exposure' therapy, he said. "Chris Kyle, while well trained in his field, had no clinical training in conducting therapeutic exposure."

It is never advisable to put someone with PTSD in an environment where there is likely to be uncontrolled exposure to provocative events -- such as gunfire and visuals of people shooting guns -- because this could stoke a flashback in the PTSD sufferer.

"This would especially not be recommended in a situation where that person had a gun in his/her hand or at least quick access to one. That would truly be a questionable activity and in this case, it was a deadly one," Rizzo wrote in an e-mail forum to journalists who were asking him about the Kyle case.

Conducting exposure therapy requires a well-trained expert clinician in a very controlled therapeutic setting, Rizzo said.

"That is very different than what one could ever reasonably expect in the atmosphere of a shooting range," he said.