Depression Support Group
Depression is a real and debilitating condition that is often misunderstood by family and friends. Its meaning can range from a prolonged period of sadness to an actual mental illness with specific symptoms. Find and share experiences with others who are going through the same struggles.

That being said, as a person fighting depression, I'd say just talk to him, but at his pace. A lot of us guys "season" our conversations with silence, so don't get concerned if he goes silent. Filling the void with conversation may shut him down rather than get him to talk.
Most of us have triggers, things that cause our depression to flare up. Often it is events such as crowds, lack of crowds, specific noises, visual images, etc. There is no single trigger that we all have.
Thank you for taking the time to try to help him! You being there with him may mean more to him than he will ever be able to tell you.
GBU
D
;-O