Break ups are never “out of tlhe blue”… I’m sure that he was thinking about ending it for a while already.
Right now he doesn’t want to be with you – harsh, but true. If he wanted to be withyou, he wouldn’t have dumped you.
The only thing you can do now is go No Contact.
If he still has any interest he will get in contact when he realises that he’s never going to hear from you again. That might be in 2 days, 2 weeks or 2 months (or more).
Effectively, you need to move on and cut contact.
If he does contact you, assume he wants to meet up and organise a date.