Boyfriend has sent an unsolicited private part pic to a girl he liked before me. What should I do?

My boyfriend (25M) liked a girl before we got together, but she never reciprocated his feelings. He told me he did a lot for her, but she just wasn't interested. Eventually, he and I met, fell in love, and have now been in a relationship for 13 months.

Recently, the best friend of the girl he liked messaged me, asking, "Are you his girlfriend?"I told my boyfriend about it, and his immediate reaction was, "Don't message her back. Remove her."

I asked him why, because I wanted to know what she had to say. But he kept insisting, "Just leave it, don't talk to her. This felt suspicious, so l pushed him for an explanation. I told him, "If there's nothing to hide, why are you so worried? If I had nothing to be guilty about, I wouldn't stop you from talking to someone." That's when he finally admitted-a few days ago, he sent an unsolicited explicit picture to the girl he used to like because he was angry at her.

This is definitely a shocking revelation. The guy always says he loves me a lot, but this act has hurt me so much. He says, he has done that in anger - but it can't be justified, right? I am completely confused, whether to give him a second chance or understand that this pattern can be repeated in the future too.

Ik, this is a serious red flag, but he has been a green flag to me ever since we met! He has loved me, respected me, like noone has. But this act surprised me, maybe he has a side I still dont know after 13 months of dating. I seriously don't know how to handle this.. I feel disgusted and unsure of what to do next. This is obviously wrong on so many levels. It is a serious boundary violation and a poor coping strategy. And also, he is still stuck on his past..it seems. Can't tell to my friends, because I know they would force me to breakup instantly but thought of asking you all first..