Bipolar rapid cycling HELP

My boyfriend very recently just started to have very severe mood swings, triggered by a stressful event involving our relationship. He would be fine one moment and the next he would break down in tears or in anger. It's been like this for about a week.

He has got very angry at me sometimes, but slowed down with taking the anger out on me. When he gets back out of the depression, and in his right mind, he apologizes and says it's not him and that he loves me and that he is so confused. This happens multiple times a day. I see the mood changes right in front of me and it's terrifying. I have depression and am medicated for it, but his is so different.

Today I went to bring him to the airport, he is going to his country to get treatment, which I am very thankful for. I won't see him for a while but I'm so glad he is getting help and going to be with his family. My last boyfriend died from suicide bc of his bipolar just last year, so as you can imagine, Im fucking terrified.

He has never worried me before, has always been so chill and normal, he has lots emotions just as part of his caring personality, but this isnt what's happening.

Does anyone have any advice on how to love and care for someone with this illness? I coach him through his episodes and it seems to help. he knows I'm with him through all of it, but I just don't know what else to do. I love him so much and I'm so afraid for him. He is so scared and I wish there was something I could say that would alleviate some of that fear. Any help from anyone with any experience would be greatly appreciated 💕