Daniel Dryden better know as Danny or Aileen is a copycat serial killer and the main antagonist of the Criminal Minds novel, Killer Profile.
Before the murders, Danny was a fashion photographer and had two sons: Kevin and Kyle Dryden. Danny eventually left his fashion job and became a crime scene photographer. Taking information from a book called Serial Killers and Mass Murderers: Profiling Why They Kill, made by Agent Jason Gideon's mentor, Max Ryan, Danny decided to become a copycat killer.
After killing a number of innocent people and finishing the serial killer section, he decided to copy The Townhouse Massacre Perpetrator, Richard Speck. After discovering that Danny was the copycat killer, he was eventually arrested by Agent David Rossi and the rest of the BAU Unit.