<human>: I've been dating my current boyfriend for 3 months now, and as it happens, we share a mutual ex. This ex is very much a romantic - both of our breakups with him were fairly messy, and it wouldn't be surprising if he still hasn't fully moved on from either of us. I've since stayed in contact with him, however my boyfriend actively avoids speaking to him. Up until last night, he did not know that my boyfriend and I have been dating at all.

Fast forward to last night; while walking around the city my boyfriend and I happened to run into this ex. We just waved, said a quick hi and moved on, and I took the opportunity to message him later on to let him know about the relationship. We figured he was going to find out eventually, and it would be preferable to have it come from us (this was something we had been planning on doing for a little while). 

His reply was extremely hostile, beginning with death wishes and finishing with me being blocked. I've looked around, and can't really find any situations that are similar to this. Our mutual ex was the only potential boundary to our relationship, and while it's nice to not have to worry about him finding out from somebody else, I feel like it may have been unfair on him to start dating in the first place.

Can you give me the gist of the text in a nutshell?
<bot>: Boyfriend and I have a mutual ex-boyfriend who hasn't taken well to our relationship. Is what we're doing alright?