Unfortunately, this has happened several times, at our local indoor range, always with rented pistols, makes a kind of sick since, if you don't own a firearm, spend your last 20 bucks to take your own life. I hate to imagine anyone that was there and witnessed it.
Now to public or private ranges, as a long time range officer, always be aware, just like life, My cop friends call it being, Fat, Dumb and happy, avoid that, keep your wits at all times, public ranges are dangerous, private ranges are less as general rule, but are no guaranty, watch those around you, if you get unconfortable, leave, don't pass go, don't collect 200$, just leave and carry on another day, I have seen sane people do dangerous things, due to lack of training, but endanger those around them. Many times.