"Every single person on that list deserves justice! And it's justice that they managed to evade!"
Schuller worked as a judge in a local court of law. In 2007, his wife, Emma, was killed in a car accident by a drunk driver, Dan Patton. On October 2008, he was diagnosed with terminal cancer. This caused him to snap completely, having witnessed so many offenders walking away. He hired Tony Mecacci, a hitman whose trial he had presided, to kill a number of people who had escaped conviction for crimes against children, Dan Patton, and then Schuller himself.
The BAU are called in after the third victim, Ben Vanderwaal, was killed. They figure that a hitman was responsible, narrowed down the list of suspects, and reach the conclusion that Schuller is the "Planner" of the murders. Almost at the same time, Schuller turns himself in, claiming full responsibility for the murders. After being manipulated by Rossi, who had known Emma when they were young, into believing he and Emma had an affair together, Schuller has an outburst, exclaiming "every single person on that list deserves justice", which led the BAU to believe there were more people on the hit list, most likely Dan Patton. In the meantime, Mecacci kills Patton and escapes. Schuller denies there being any more people on the hit list. He is then arrested under the public pretense that he is aiding the investigation. As he is brought out, he confesses to Rossi that he had lied earlier. He is then shot and killed by Mecacci, apparently from a sniper position.
Each mutilation represents the crimes the unsubs believe the victims had committed. Schuller was profiled as "The Planner" of the killing team, both of whom are males. The Planner works in the criminal justice system, working as possibly a defense or prosecution attorney, a judge, or even a police officer. It is possible he suffered a severe and devastating tragedy of some sort. Because of the sophisticated nature of the scenario, the planner is probably aged in his late 50s to early 60s. The Planner likely met the second unsub, named by the BAU as "The Enforcer", within the court system. The Planner hired him to carry out justice where the courts did not. This kind of justice does not come cheap, so he has good access to substantial money. There was absolutely no attempt to hide the mutilation, which suggests that the Planner does not care what the authorities find or he wants them to find it, but the Enforcer has no such intentions.