TORONTO - A new book about former colonel Russell Williams says police found child porn on his computer but laid no charges in exchange for him pleading guilty to murder and sexual assault.

"A New Kind of Monster," written by Globe and Mail reporter Timothy Appleby, says the convicted killer wouldn't admit to downloading pictures of teenaged girls in sexual positions.

A source quoted in the book says Russell couldn't face the stigma attached to child pornography, though he was willing to plead guilty to murder, rape and a series of bizarre sexually motivated break-ins.

The book argues that Russell's sense of shame, strong emotions and close personal attachments set him apart from most serial killers.

The former commander of Canada's largest military airfield pleaded guilty in October to two counts of first-degree murder, two counts each of sexual assault and forcible confinement, and 82 break and enters that date back to 2007.

Williams faces life in prison with no chance of parole for 25 years.