I'm so sorry this happened. He's 16 years old and it's not that unusual for teenagers to try drinking. However, after everything you have all been going through, I can see how it would cause you to question it.
I don't really have any advice to give you, but please know that we care about you and your children. Hopefully, this is just a stupid stunt and the way he's feeling and will feel in the morning will be enough to make him decide that drinking isn't such a great thing. (((HUGS)))