The 2013 slaying of a beloved businessman in Washington state helped federal officials not just uncover another man’s disappearance some 800 miles away, but led them to a group of violent men ...

Find out why Joseph O’Boyle brutally killed his doctor, beloved chiropractor James Sowa, in his Bensalem, Pennsylvania, home, and how detectives found him.

Learn more about the investigation into Michigan man Trent Mallory's 2014 murder, as told in Oxygen's Killer Relationship.

What happened to the Memphis businessman?

Season 3 Preview: "Trader Trent's" following on Facebook Marketplace opened up a range of possibilities for detectives.

Detectives reveal the weather was vital in Trent Mallory’s case.

Preview: It is quickly discovered that Carmela Knight died from blunt-force trauma before being badly burned in a house fire.

Preview: Carmela Knight, a "suburban hockey mom", was found dead after a house fire surrounded by drug paraphernalia. What happened?

Friends and family tearfully recall the night that led to Carmela Knight's death.

Dr. Jim Sowa is killed by his patient, Joey O'Boyle, who had a history of violence and mental health struggles.

Investigators find a partially packed suitcase in Joey O'Boyle's home.

After Uloma Curry-Walker's frantic 911 call, firefighters on the scene recognize Lt. William Walker, a fellow firefighter.