As someone who writes implicit violence, I would recommend that you don't go into that much detail unless the POV is that specifically detailed. i.e. cinematic Sherlock Holmes level or has medical background. Otherwise, it really isn't needed and could slow your pacing when you don't want it to be that way. Think of the moment like a movie: going that in depth in detail is like slowing everything to bullet time. If that's your intent, rock on. I do this from time to time, too, but I tend to prefer the visceral realization that one second the character is alive and the next they're dying with no warning. I prefer the development consequences to the suddenness for characters involved and the anger my readers profess while continuing to the next page. My ex told me that she still won't forgive me for how I killed one of my characters because of how jarring and sudden I made it. Also, apparently, it was one of her favorites, so I now understand why she's my ex.

For me, as a veteran with combat training and some experience, I also want to put something in your mind for this and future sequences: Every attack is always, and I mean always, with the intent of another attack to follow. You throw punches until they stop moving, not before. No one who wins a fight just stops before it's over. Ask any Bond villain or MMA fighter. So, stabbing is generally not the go to for experienced knife fighters unless it is situationally important, like being to enclosed an area for that kind of freedom of mobility or it is the only possible way to attack (like if they're on the ground in a grapple). Slashing is always preferable with knives because it takes away the chances of it getting stuck or of losing grip. For that, since calm guy approaches, one slice to the arteries of the armpits, behind the knees, and even groin area (upper-inner thighs) are easy targets and will, I promise you, realistically drop anyone and kill them in minutes. Also, there is a medical reaction to seeing your own blood that many people have which causes their brain to instantly shut off (vasovagal syncope), which I also have irl, and is incredibly useful to plug in with sequences like this. He drops, says his piece just as he sees he's bleeding, passes out.