Kristen Gilbert was born in Massachusetts in 1967 and had a troubled childhood, physically and verbally abusing her boyfriends. She graduated from nursing school and got a job at a veterans hospital, where she killed patients and was nicknamed the "Angel of Death." Gilbert killed through injection of epinephrine and was convicted of four murders. As a skilled nurse, she was able to hide her crimes for years before coworkers reported suspicions that led to her arrest and conviction.