Police tried to keep Hicks' phone number a secret from Stimon, but it frequently needed to be changed as Stimon would figure it out and harass Hicks, Comer said.
In November police caught Stimon slashing Hicks' car tires near her home. He was arrested and charged with destruction of property, stalking, and violating the protective order Hicks had filed against him.
"What was so devastating to Mr. Stimon was that when he was caught, his computer and cell phone were in his car, and they became evidence," said Shurtz.
Watch the full story on "20/20: The Ultimate Betrayal" Friday at 10 ET