Why would my husband of three years just walk out on our marriage after my mom died?

So my mother passed away a year ago (it will be two years this December) and he was very supportive and comforted me. For the past four months, our marriage has been on the rocks. My husband said I have changed and I need to get over the death of my mother. We’ve been fighting for four weeks, he hasn’t been home and been staying at his friends house. I am just stressed out. We have a two year old son to take care of. I was hoping we would work things out but he said he can’t live with an overbearing grieving wife that cries for her mommy. I don’t need to be nice to you anymore! Yesterday he completely left. He left without saying a word and I am crushed. He’s been acting like an ass since my mom died. He was supposed to pick up our son from Day Care at 2:30pm but instead he packed his things and left. So I had to leave work to pick him up.
I am 26 with a two year old baby with me.

Why would my husband of three years just walk out on our marriage after my mom died?
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