Mackenzie Shirilla unloaded on her boyfriend Dominic Russo in a super toxic text chain years before she was convicted of murdering him ... and the messages offer a peek inside their strained relationship. The text messages, obtained by TMZ, were part of the police investigation into Mackenzie's fatal car crash that killed Dominic and their friend, Davion Flanagan . Mackenzie appears super emotional in her texts ... telling Dominic, "I'm gonna kill someone" ... "I j want to bang my head on the