Donald Harvey is seen as a good worker but he is in fact a serial killer who confesses to multiple murders - but no one initially believes him.

Nurse Charles Cullen says he hated to see people suffer but he became the most prolific serial killer in New Jersey history.

A rising pop star, Selena Quintanilla, is gunned down by her fan-turned-manager, Yolanda Saldivar. What led to this tragic betrayal?