Very sad.

Thats crazy with a #6, wonder if he hit something in the water to cause damage like that, looks like the boat may have sank if it didnt end up on the pontoon. I really wouldnt think failure in the drive would break the "box".

May have hit something. I've seen whole trees floating just below the surface on Great Lakes waters. No doubt that mechanical failure was the cause of initial accident, ejection and death and not wearing lanyard cost a man his leg.

What a tragic accident that could have had a little better ending if only a simple lanyard was worn.

And possibly life jacket/s

I have video of the incident. I'm no expert but it appears to me some other type of malfunction caused the spin. Weather steering, negative trim or tunnel tab. The boat crosses the pontoon wake riding nice and aired out. As soon as it crosses wake it appears to suddenly drive very wet and sponson steer to the right for about 1.5 seconds. Before the ass end drives around the front and spins. I'd say the box shattered from force of the spin and the force of the water on the big #6. the drive being ripped off at a 80 mph sudden 90 degree turn. Similar to the strong forces on the stihl skater that ripped his complete drive off.

The pontoon was helping for sure and may have saved the other two passengers lives as they were directly in the path of the cat before they intervened. One of the pontoon passengers jumped off the pontoon into the water to help the floating victims it appears, causing him to be struck by the prop as the cat was still powered up and driving the pontoon In circles for another minute or so

Absolutely correct, but maybe I can add some important details. First, the rope / line should be polypropylene because it floats. Second - and even more important - make sure neither end of the line is attached to anything as you drop it and get the hell out of the way. There are videos of folks doing everything correct except this - and getting sucked right into the out of control boat. Done correctly, the floating line trick should disable a boat enough so that one can - carefully - approach it and shut it down. Be careful though. Sometimes the boat will have enough power to part the line after a few seconds and go right back to circling.

Remember, the first rule of helping somebody in distress is not to get killed yourself.

So sorry to hear about this tragedy for everybody involved.... I'm not going to speculate on things but will add to some comments already made here.

Wear the safety lanyard. we all know these work and will shut off the motors.
Wear proper PFDs. The type rated for impact at speed. If you get thrown from a boat a proper pfd will both keep you afloat and will also protect your body from impact. The little auto inflate ones will keep you cool while running, but offer no such impact protection.
Prop fouler, yes it can work if the proper floating type of line is used which is strong enough to jam up the propeller. Anybody who has watched "Whale Wars" would be familiar with how they work.
Ramming the out of control boat would work, although much more dangerous.
As Too Stroked said, the safety of any rescue people comes first. This is taught in any water rescue course, individual and team safety comes first. You do nobody any good if you die or become a victim yourself.

Notice in the picture posted above, that the Port side skeg is broken off. This could happen in a spin, due to collision, or perhaps when being towed in and dragging the bottom.
I'm sure Brad @ PBN can figure out what happened if he sees the video.