I have always thought mounting a light on a handgun was a VERY BAD idea, since it becomes real easy to think of your gun-mounted light as a general purpose flashlight, instead of an aiming device for your firearm. Flashlights and guns serve different purposes, and trying to combine the two will inevitably lead to tragic results like the incident described.
I have the same problem with guys who use their riflescopes as spotting scopes, and I've seen that done frequently. The riflescope is intended only to aim the rifle, not to scout for game or look at other interesting objects. That's what a spotting scope or binoculars are for. When you're looking through the scope, you're not watching where the muzzle is moving, and that could lead to tragic consequences.
I have the same problem with guys who use their riflescopes as spotting scopes, and I've seen that done frequently. The riflescope is intended only to aim the rifle, not to scout for game or look at other interesting objects. That's what a spotting scope or binoculars are for. When you're looking through the scope, you're not watching where the muzzle is moving, and that could lead to tragic consequences.