OBVIOUSLY the moron isn't stable in the first place or he wouldn't have been shouting at his computer while waving a replica firearm around!! Hello, McFly!
Maybe it's just me, but it doesn't seem that stability can be accurately determined from these particular manifestations of frustration over a stubborn computer. Many are the times that I've seen people become profoundly unhappy with their computer to the point of yelling, and some would no doubt have drawn down on their monitor with a replica gun (something they know will do no real harm) had one been available. But I don't have a psych degree, and I don't claim to be an expert.
Still, it's one thing to practice point-shooting your monitor with an airsoft everytime you get BSoDed, and another to do so only partially in sight of witnesses.
Sometimes eager citizens do more harm than good, though.
I remember a case not to long ago where a man came stumbling home drunk. He couldn't find his keys, so he climbed in through a window (his own home, mind you - nothing wrong with that). A neighbor spotted him and called the cops. It seems that there was a possibility that the neighbor had recognized him, but was just giving him a hard time.
Anyway, police burst into the guy's home with the intent of stopping a criminal. The guy jumps out of bed still intoxicated and sees a group of men running into his bedroom, so he grabs a knife and goes at them. Cops shoot, man dies.
Everyone ('cept maybe the "concerned neighbor") was acting appropriately based on their knowledge of the situation and with the best intentions. The man was trying to defend his home against intruders, the police were trying to stop a potential robbery and then trying to defend their own lives.
This was discussed at length on TFL.
Bad calls can lead to bad situations without cops always being JBTs.
This was a bad situation that could have been much worse had the SWAT been a bit more trigger-happy. The cops seemed to do very well, all told. Without knowing if the gentleman was pressured into giving up his firearm and if he will get it back, I won't judge that.