Stacie,
Before you kill the fish, I would let him go for a day or so and see if his jaw goes back in place. I would also net him and look in his mouth. I had a female Ps. multicolor who I thought had a mouth full of eggs for about two weeks. She didn't eat while in this condition and I thought she was just brooding eggs. After two weeks, I looked and I couldn't see any fry in her mouth. So I got her out to strip her and I looked in her mouth and there was a piece of gravel stuck in her mouth. I took a tweezers and pulled it out. She is doing fine. In my years of owning a pet shop, this was common with goldfish getting gravel stuck in their mouths.
Also, if there isn't anything in his mouth, I would gently pull on his lips and see if his jaw resets. This is another possibility that I have encountered with cichlids over the years. Bag him up and bring him to the meeting and let a few people take a look at him.
If you need to euthanize the fish, there are some people who do it like Mike said by putting the fish in the freezer. I personally use very hot water and drop them in.
Lonny
