at the house. then, just a few hours later, the house is up in flames. the three adults, found dead in the home, stabbed and doused with gasoline. and the child found burned in his bedroom. authorities now believe wint was the man seen running near the family's burned-out porsche in this surveillance video. he's an angry, troubled man, relatives say. >> he's very hostile. he's arrogant. he doesn't listen. >> reporter: wint has a long rap sheet, including arrests for assault and domestic violence. that criminal history led to his identification. abc news obtaining exclusive details from this lab that tracked him down from dna left on a pizza crust of that domino's pizza, ordered that fateful night. >> because of that the evidence that we got, we were able to get a hit on a dna match. >> reporter: it's not known whether he acted alone, but today, we learned wint was no stranger to the savopoulos family and their business. this is american iron works. savvas savopoulos was the ceo. and police believe that daron