Any person has a right to end any relationship at any time for any reason. Maybe he wasn't as into you as you thought. Maybe he met someone else. Maybe he thought you were too needy. Maybe he's a selfish jerk who wants what he wants when he wants it.
If you're looking for permission to get him back "by any means necessary", this isn't the place to find it. Maybe start working on your own insecurity issues and let this guy go with dignity.
Welcome, by the way. And sorry if any of that sounded harsh. I've been in your shoes and felt what you're feeling and after working on myself for awhile, I've come to realize that those feelings were about me, not about the other person.