I think he's been a "person of interest" for some time. Once they made the connection to that bar, they investigated the employees, and discovered his parole violation. He was taken into custody for that parole violation, and they were able to get a DNA sample, which they matched to blood they found on the plastic ties used to bind her hands behind her back. He is also a possible suspect in several other rapes.
They said there was evidence of a "BTK" like scenario - the tape used to bind her head was vertical, not wrapped horizontally like you think someone would have done it. It's just so sad and awful.
I have to wonder if something happened between the two of them in that bar that triggered his rage response - aren't many rapes a result of rage, not just a sex crime??