(CBS/AP) Investigators who have compiled mounds of evidence against Steven Pieper are adding incriminating text messages to the case against the 21-year-old, who pleaded guilty Tuesday to second-degree murder in the death of his ex-girlfriend Jenni Lyn-Watson in upstate New York.
Onondaga County District Attorney William Fitzpatrick told CNN that although investigators were unable to recover Watson's cell phone, they were able to review calls and text messages made by the 20-year-old victim, as well as by Pieper.
While reviewing text messages sent from Watson's cell phone, investigators say they came across the shorthand "GTG" or "got to go" which is an acronym not typically used by the victim, but frequently used by Pieper.
After looking at Pieper's phone which was left at Watson's home in Liverpool, a suburb of Syracuse, the day of the murder, police came to the conclusion that the defendant had sent the text to a mutual friend of theirs pretending to be Watson in order to cover up the crime, reports CNN.
Pieper confessed to the crime in detail during his grand jury testimony Tuesday. He told the grand jury that after strangling Watson to death in her parents' home on November 19, he carried her out to his car and put her body in the trunk in broad daylight. As he was leaving the scene he was stopped by a sheriff's deputy because he did not have a front license plate, CBS affiliate WTVH reported.
The deputy did not discover Jenni-Lyn's body but it was enough of a close call to scare Pieper into dumping her body at a nearby park, in a swampy wooded area, attempting to cover it with vegetation, according to The Syracuse Post-Standard.
Jenni-Lyn was home for Thanksgiving from Mercyhurst College in Pennsylvania when she was murdered.
Searchers found her body eight days later, and Pieper was arrested shortly after.
Pieper struck a plea deal and is expected to be sentenced to 23 years to life in prison on March 8.