Pranks and jokes are meant to be harmless and make people laugh. This kind of prank was not harmless and not a laughing matter.

You say he knew that you would believe him. So he knew that you'd take it seriously and probably be hurt, even for a few seconds.

At best, it was reckless and immature. At worst, it was an intentional way to mess with your emotions and hurt you. I've had a friend who did this to her boyfriend, and I think it was her way of "testing" how he'd react, to see how upset he became/how much he cared for her. It's pretty messed up. Pretending to break up with someone is never okay, April Fools Day or not.

I would say to talk to him. Explain exactly how it made you feel. See how he reacts, and listen to what his intentions were.