Most Helpful Guy
First and foremost; it's very important to give him the required space. The grieving process is a stage that must be proceeded step by step. The emotions must be released via the grieving stage.
What you can do is to be there for him. Be available. Words can do magic. Express yourself and make him aware that you are there. That he can call on you if he needs anything. Check on him once in a while. Cook something he likes; get him to get some fresh air and walk together; try to get him into the places that would change his mood to the good.
Be there and be available. Pursuit pleasant and refreshing activities. Do it all considering his personal space.
Additionally; if he reacted unusual; overreacting and shouting or any similar unusual behaviors; don't get upset. People grieve differently and misunderstandings are so common when someone having emotional imbalances and shock. Just be there. Being there is one of the biggest things that someone can do for another.
Most Helpful Girl
You can't really do much for him other than being there for him. The only thing that will help is the passage of time. In the meantime you can take care of him and make sure he doesn't feel too lonely or depressed.