Husband randomly sends a text to separate last week and has cancer?

i feel hurt and haven't told the kids. im making a temporary accnt to post this. Married for 15 years, 2 children, thought we had a long time together and we would grow older together until he randomly decided to leave on a random Tuesday night. We're older now of course, early 40's but sometimes joke about having another child.

Texts me a message and a paragraph about how he appreciates me and wishes the best for me and the kids, and says that he needs to seperate on Tuesday afternoon, then that evening comes home and kisses the kids, takes some of his stuff and leaves. Refuses to elaborate. After looking into it for like an hour, found out he has Cancer and never told me or the kids. I feel hurt he wanted to seperate, but he also couldn't tell me this. He's rented out an apartment and hasn't come home since Tuesday and is being incredibly dry on the messages. I remember when his father died, he showed practically no emotion just being quiet, but he isn't an emotionless person, in fact a kind one which is why I feel hurt. Anyone else dealt with this? Am I wrong to feel hurt that he doesn't wanna spend his time sick with me?