Donnie Mallick

Donald Allen Mallick better know as Donnie Mallick is a serial killer and the main antagonist in the Criminal Minds episode, Nelson's Sparrow. He is also the secondary antagonist of season 10.

Early Life and First Murders
Donnie was sent to his bird-loving and wheelchair-ridden aunt Gertie Mallick due to his schizophreniac mother Zettie Mallick being sent to a mental hospital. Years later, Gertie died and Donnie became the sole resident of Gertie's house, for unknown reasons he started kidnapping women and breaking their legs and later bounding them to wheelchairs, just like his late aunt. Days after kidnapping them, he would kill and hide their bodies in a nearby forest. After Tara Barnett was kidnapped by him, her mother Mary Allen sent BAU Agents Jason Gideon and David Rossi to find Tara and arrest Donnie for his crimes, which resulted in a failed attempt to find him. Tara stayed with Donnie for 37 years until her death by cancer.

Return and Killing Jason Gideon
Tara's body was found by the local, caught the atention of Gideon, Gideon started a investigation without the help of the BAU Unit, which unfortunaley caused his death by the hands of Donnie himself. However, killing Gideon unitentonally caught the attention of the BAU Unit.

Death
Donnie eventually returned to his role as a serial killer, he tricks a woman named Josie Behdart and locks her in his basement, breaking her legs in the process. Fortunaley, Donnie was found by the BAU Unit and was ambushed by them, while at his backyard, he is tricked by Rossi, who tells him that he would become more popular in prison if another FBI Agent is killed by him, Donnie then grabs his gun to shot Rossi but is gunned down by him.