The fact that you (an average US citizen, presumably) think tasing is de-escalation is literally part of the problem.

I was trained by US cops multiple times during my 10 years of security work. Sadly, I didn't receive much for de-escalation training. I had to learn it myself. Oh sure sometimes escalation (like sounding intimidating while moving your hand to your hip) worked as a method of de-escalation, most of the time it was to reinforce the mantra to "ensure you go home at night".

Tasers aren't even non-lethal, they are now (properly, with public outcry) considered "less lethal". No pepper spray or mace mentioned, no trip attacks, no net, no means of incapacitating him before reaching to the nearest gun-like object.

Meanwhile, we have no one there to assess him to determine what his medical and/or psychological needs are, because "he's dangerous".

The cops brought the rifle.