This would be what we in NFHS call a flagrant foul. But we don't have a signal for it. I'd prefer to have a signal, but I'm not on the rules committee.

Fortunately I've only called one flagrant in my career (in a recent 3 on 3 tournament), but the mechanic I've seen and would use is the "cross and toss". The intentional mechanic followed by a point to the showers.

My experience with the flagrant fouls was that I really didn't have time to focus on making up a mechanic for it. I blew whistle and focussed on stopping the chaos. The players were then sent to their bench while my partner and I discussed what happened and what we're going to do about it. Then we walked to the table and explained to the table and both coaches what the call is. There wasn't much need for a mechanic, to be honest.

Now that I've passed the 2000 mark, I can contradict myself with abandon. :)

I feel like I'm almost half the man you are (920 right here), but then we worked together enough that I already knew that.

Hey, that's a cheap shot. True, but cheap. ;)