Mark Wells, who was convicted of four murders in Ontario, Canada, died Saturday of natural causes. He was 42.
Wells was in the process of killing Annette Norman when her sons Richard, 8, and Christopher, 7, walked in and witnessed the crime. Wells stabbed the boys and then slit their throats (one of the boys was still holding a bag of candy when his body was found).
Wells was also found guilty of strangling Christine Tansley, whose body was found in her blood-spattered apartment the day before the Norman murders.
Wells started serving his life sentence in Ontario in 1991 but was moved to the Matsqui Institution in British Columbia to receive treatment for a lengthy terminal illness, and to be closer to his relatives.