India, May 25 -- Years before Mackenzie Shirilla was convicted of murdering her boyfriend, the two had a deeply troubled relationship and a series of disturbing text messages are now offering a rare look inside it.

The text messages, obtained by TMZ, were part of the police investigation into the fatal car crash that killed Dominic Russo and their friend Davion Flanagan. In the messages, Mackenzie comes across as highly emotional and unstable. She told Dominic, "I'm gonna kill someone," "I j want to bang my head on the wall till I'm dead," and "THIS IS WHY I J WANNA F***ING KMS," according to TMZ.

Other messages show Mackenzie discussing not being pregnant, getting tested for STDs, dealing with health issues from smoking, feeling depres...