Remember you're dealing with a loaded firearm
There's a round stuck in the chamber.
1) Point it in a safe direction.
2) Keep your finger off the trigger.
3) Remove the magazine.
4) Place into a padded vise. You may have to use wood blocks and remove the grips too.
5) Once its in the vise, stand behind it and, keeping the finger off the trigger, use both hands to pull the slide back. If it doesn't come back, get a 2 x 4 and place it against the muzzle. Tap with a plastic mallet, rubber mallet or copper/brass mallet. Be sure your hands are below the muzzle. A little tapping should be able to get the slide to move back and eject the cartridge.
ETA: If you're uncertain about it, you might want to hose the primer down with WD-40 for a few days in the roll. That should help deactivate the primer.
