Oh no! That's terrible, I'm so sorry to hear that. My family has some chickens of our own as pets, I can only imagine how shocking this all is. People can be so cruel.

I honestly don't have suggestions other than what you've probably already considered; keeping him distracted with other activities that won't stress him out too much, just generally being there for him...Although my brother doesn't have depression, he has ADHD and anxiety; when he was younger, we would take him out to the movies or go out and enjoy nature through hiking, it seemed to alleviate some of his lows by not allowing him to ruminate too much. I don't know if either of these things would work well for your son since everyone's got different circumstances.

Again, I'm so sorry for your loss. My thoughts go out to you and your family.