How do you help a significant other with loss?

Alright, well, my name is Alison, and I am 24. I just recently got engaged to my fiancé, Christoph, who is 33. He is the sweetest man I have ever met, and he treats me so well. He is so charming, and he is such a gentleman. Well, he was very close to his father when he was younger, but he passed away when Christoph was only 15 years old. His father was a policeman, and I think that influenced Christoph a lot, because he is a bail enforcement agent now (basically a bounty hunter) and he takes great pride in what he does. Anyways, after his father passed, he became very close to his mother. He is an only child, so it was just him and his mom for a long time. Well, Sunday night, we went over her place to visit her, and found that she had killed herself. Christoph was completely distraught (understandably) and inconsolable. She never showed any sign of depression, and now Christoph says he feels like he’s responsible for her death because he never did anything to help her. He insists that this is his fault and that he was a bad son. Every Sunday morning, he would buy both his mother and I flowers and we would bring them over to her when she came back from church, and he spent loads of time with her so she wouldn’t get lonely. I have never seen such a good son.
Anyway, he was given some time off of work, since performing a job like his in such a state could be dangerous for him. He has spent a lot of time just laying on the couch staring off into space. I don’t know what to do for him. I suggested to him that we go for a walk or do something and he just told me he didn’t feel up to it. Again, understandable. I made him his favorite foods and spent a lot of time just sitting with him. Last night he refused to come to bed, and he fell asleep on the couch at around 3 am and he was up by 6 am. I’m just worried about him, and I want to help, but I don’t want to pester him. What can I do? It’s killing me seeing him like this… How can I help him through this?