Why would a guy randomly block you?

Me and this guy used to date. And we haven’t been friends on Facebook or talked since we split almost a month ago and I noticed he randomly blocked me?

I don’t message him or bother him so I don't know why he’d just block me out of no where? I wasn’t blocked yesterday, but now today I am.. The only reason I noticed was because yesterday a mutual tagged him in a picture, and today it doesn’t show his name blue..
Why would a guy randomly block you?
Post Opinion