Boyfriend (20M) did something very scary to me (21F) any advice on how to handle this?

My partner M20 recently lost a vital family member in a horrible accident. The following weeks after this I F21 took care of him as much as I could, taking time off of work to do so. About two weeks after after the passing, I was sitting in my partners bedroom and he left. I later heard a creek at the door and saw a shotgun opening the door, without seeing a face behind it I immediately got scared. Some background info: My partner knows how uncomfortable guns make me, I don’t like to see his guns, hear about them, have it at my house, etc.. it’s just my own personal feelings and opinions. He’s known this through the 4 years we’ve been together. Back to the story, I saw him emerge as well, holding up the shot gun which he previously in the week told me he inherited from the deceased family member (not pointed at me but at the wall adjacent to me). He’d asked me previously if I wanted to see it to which I declined. I was in shock and confused why he would even bring this gun in his room, but then he cocked and shot the gun straight ahead. I was about 5 feet away on the bed and it went through the wall. My eardrums were blown and I couldn’t hear, I just smelt smoke and curled up in a ball crying and I think screaming. Long story short he profusely apologized stating he did not know the gun was loaded and has never handled a shot gun before. And was incredibly sorry and seemed shocked himself. I’ve had nightmares about this ever since and loud sounds set me off. We didn’t have a further conversation about it because the scenario was pretty troublesome considering he’d just recently lost someone. I did end up talking to him about it a week or so ago, mostly wondering why he even brought the gun in the room at all to which he said he didn’t know and wasn’t thinking. This scares me a bit… he again apologized saying he didn’t deserve me and he truly didn’t know it was loaded and would never point a gun at me and it would never happen again. And that he learned from his mistake. I’m unsure if we need some time apart.. it feels conflicting because other than this our relationship has been good for the past 4 years.

EDIT: To add some info he had unloaded it earlier in the week and his dad reloaded it without his knowledge. I felt that afterwards he didn’t take it as seriously as he should’ve (the following weeks), however I’ve been struggling because of the fact that this was freshly after he lost a vital family member. He did just start therapy but I wanted to make this to see others opinions. I know this is silly but we’ve been together for so long that It’s scary to think of separating. It is more so the fact that he brought in the gun especially in the context of holding it up knowing how uncomfortable they make me.

EDIT 2: Since this he has taken a gun safety class if that makes a difference.