People grieve in their own ways. It can take many forms. You didn’t mention how long this has been going on. If for only a week, your husband may be just needing to withdraw from life for a bit in order to get his bearings again. It’s not unusual when someone has lost someone who has been particularly important and loved to want to stop the world and get off for awhile.
Generally grieving lessens as time passes and people do get on with life — even while still having some moments where the loss hits again, painfully but in a way that can be managed. This can go on for quite awhile but it doesn’t interfere with day to day life.
But if his grieving goes on for so long that your husband can’t work or go to school or talk to anyone, he may be suffering from what is called complicated grief (sometimes called persistent complex bereavement disorder). In such cases, the grieving is so intense that it prevents the person from healing and moving on.
It’s all about timing. If your husband has been withdrawn for just a week, give him space, let him know you love him and that you are there for him. Take the lead from him. Don’t take it personally if he doesn’t have it in him to be there for you right now. But if it goes on for weeks and weeks, then it’s time to be concerned and to urge him to see a grief counselor to help him through this very difficult time.
I wish you well.