What should I have done? SH Trigger warning

My neighbor is a great man. He’s always been extremely friendly to us and is very religious, he’s older in his 50s I would say. He is an ex-marine.

Today, we come home and he walked out of his house as I was getting out of the truck. He looked at me but something was off, I smiled at him as usual and he would typically smile and start conversation. Today, he just starred at me and his eyes and facial expression was off, he was blank. I looked down and he had a knife in his hand and something black in the other hand, I assumed it was like a knife case or pouch. He was pacing back and fourth around his hard and in the driveway. I go inside first because I’m 7 months pregnant and I can’t lift our toddlers anymore. We have an almost 3 year old and almost 2 year old. I waited for my husband in the yard and told him what I saw and said I wanted to get my other son first because usually he gets 1 out at a time since I can’t lift them but I didn’t want anyone left in the truck even for the 30 seconds it would’ve taken for my husband to bring 1 inside.

Well, we went inside and I told my husband I was super concerned and he said he was probably just angry about something but that he was nervous as well. The cops ended up being called because apparently in the other hand it wasn’t a case/pouch, it was a gun. He put it to his head and then the cops got there. So he was walking around with a gun and knife, pacing his yard. I feel so bad now. I’m not sure what I should’ve done in the situation? Or if it were to happen again? Asked if he was okay? Tried to talk to him? I just was scared because my kids were outside…