I read that Huffington Post was trying to promote that we don’t know whether he was Muslim or not.
I guess they didn’t get the memo. I heard his relative, cousin I believe; say he was always a Muslim when asked if he had converted.
Yesterday a video of him in a store was posted. IIRC, the Muslim owner reported that Hasan berated him for not going to the mosque enough.
That’s enough to convince me he is Muslim. Not to mention that he was dressed in Muslim garb.