Mayhem was born Dean Gerard Winters, via Super Stars Bio. A native New Yorker and character actor, Dean Winters his first appearance on national television with the NBC cop drama "Homicide: Life on the Street." After playing Tom Marans in three episodes, "Tom Fontana ended up writing the part for me on Oz", Winters tells the AVClub. The part he's referring to is the dramatic role as Ryan O'Reily on the HBO prison drama "Oz" from 1997-2003. 

Winters may have been introduced to American cable subscribers as a homicidal sociopath, but he soon got to play on both sides of the law. While playing an inmate, Winters was also playing Detective Brian Cassidy on the NBC drama, "Law and Order: Special Victims Unit" (via IMDb). After two seasons, Detective Cassidy decides that he isn't cut out for the sensitive and heartbreaking nature of the SVU. But because SVU fans love him, Cassidy is a recurring character in later seasons of the TV series, per PopCulture.

Once "Oz" ended, Winters picked up another gig as an NYPD detective — this time playing Johnny Gavin, brother to Denis Leary's Tommy Gavin on the Fox series "Rescue Me."

After all of the hard and heavy dramatic performances, Winters got to flex his comedic muscles as Dennis Duffy, Liz Lemon's sleazy sometime-boyfriend, as well as Detective Jake Peralta's foil, Detective "The Vulture" Pembroke, in the comedic series, "Brooklyn Nine-Nine."