Investigators and prosecutors have also revealed shocking new details about the murder in which Shiavo was charged.
"She was actually stabbed more than a dozen times," Det. Lt. Jack Fitzpatrick.
That woman, 61-year old Nancy McKinley, was staying with her friend when she became the victim of a what police say was a random burglary that for some unknown reason turned violent.
"He was aware that somebody was in there. He was aware that they were awake and yet he went into that room and confronted her," Fitzpatrick said.
Police say he noticed a light go off an on in the victim's bedroom. That's when Shiavo allegedly grabbed an 8 inch knife.
The victim, a former librarian, was the wife of a former U.S. ambassador to Haiti and longtime diplomat.
Police say Shiavo's name came up in the investigation of another burglary in the same area.
That and other clues led them to his home in Medford, where his arrest surprised neighbors.
Evidence teams found the murder weapon at the scene where they were still at work on Monday evening.
NEW YORK AND TRI-STATE AREA NEWS