So I tracked down the whole story....
1. It is unlikely that the victim was a Trump supporter. He was not named, but was described as mentally disabled.
2. It is also unlikely that the four who kidnapped and tortured him were voters at all...
http://www.fox32chicago.com/news/crime/charges-filed-in-beating-of-man-on-facebook-live
Jordan hill was 20 when sentenced to 8 years in prison for the beating...Let me know if you find evidence that he was registered to vote.