The bad guy has got a stick. Get in close, avoid the initial strike. Soften them up with some knees and elbows. Wrap up the head and take a guillotine choke while continuing to throw knee kicks. Control the stick arm with your free hand.
Now that you’ve got them in a fairly weak position, tighten up the choke, summon up a firm voice and then say “I need you to drop the stick.” If they don’t comply, tighten the choke and deliver some more knee kicks. If there’s a wall near by, slam them into the wall so they can’t squirm around as much. Then tell them again to drop the stick. Hopefully this time they drop the stick.
Assuming they drop the stick, then say “I need you to lay down on the ground on your stomach”. Keep control by helping them down with your knees and elbows. Once they’ve gotten onto their stomach and you have a firm knee in their back to keep them there, pull out your cell phone and dial 911.
It’s an ideal scenario, but you get the idea. If you’ve got the bad guy severely compromised, order them around into a place where you can control the situation (knee on their back) and then solve the problem (call the police). Communicate. This was the scenario for today’s adult class. Get control with your body then try controlling them with your voice.
Incidentally, if they don’t comply when you ask them to drop the stick, make sure you’ve got a solid blood choke and make them pass out. When they pass out, they’ll drop the stick. Don’t hold onto the choke for more than 10 seconds after they pass out or bad things happen. Get them on the ground, kick the weapon away, sit on them and call the police.