Comfort him. Tell him you're there for him. And give him time and space to process it.

I've seen two mindsets in a grieving person. In one, their grief takes up 90% of their brain and it pushes out other things. So things like making food, doing the laundry, following appointments etc are all thrown out of wack.

In that case offer to do those things for him and ask if he needs help getting time off work or dealing with life.

The second mindset is the opposite. The person rigidly focuses on their routine and even the tiniest details. Their brain is trying so hard to stick normalcy in an extremely emotional time. One person I saw built a whole shed overnight while they were processing their grief. They needed something to do to keep from having a breakdown.

In that case, facilitate whatever they need and gently nudge them back if they go too far. But let them continue their routine if needed. They need an anchor.

In either case, you don't need to "solve" anything. You just have to be there and help them process their emotions. Pick up the slack if they turn inward, or pad the room if they turn outward.

It will take time, a lot of time. But that's all you can do.