The caretaker who first raised the alarm when he spotted triple-killer Stephen Griffiths on CCTV shooting a woman with a crossbow has said those images "will stay with me for the rest of my life".
Griffiths - who called himself the "crossbow cannibal" - was arrested after Peter Gee called police in May after he watched the shocking footage.
Leeds Crown Court heard on Tuesday how the 53-year-old caretaker was reviewing weekend CCTV tapes when he came across images of a woman running from the postgraduate student's Bradford flat.
The footage then showed Griffiths get a crossbow and fire it at the woman, who turned out to be missing prostitute Suzanne Blamires. He then made a one-finger gesture towards the camera.
Griffiths, 40, was jailed for life on Tuesday for the murder of Miss Blamires, 36, as well as two other prostitutes - Shelley Armitage, 31, and Susan Rushworth, 43.
He was told he will never be released from prison by a judge who heard shocking details of how the women were killed, dismembered and even eaten.
Mr Gee told The Sun: "What I saw on that tape horrified and distressed me. Those images will stay with me for the rest of my life."
The caretaker added: "That day changed my life forever."
After Griffiths was sentenced, the detective who led the inquiry, Detective Superintendent Sukhbir Singh, was asked whether officers would ever have caught Griffiths without Mr Gee's vigilance. The detective said he believed West Yorkshire Police would still have tracked him down.
Mr Gee's comments come amid continued speculation about whether Griffiths, who was a PhD student studying murder in Victorian Bradford, has killed more people.