On the night of August 17, 2014, a party at the Stadium Housing Project in Lawrence, Massachusetts, ended in tragedy when gunfire erupted. Mark Trussell, 35, a father of four, was an innocent bystander who was struck in the back of the head after a gunman fired into the crowd. He was airlifted to a Boston hospital and died a few days later.

Investigators say the shooting began as an act of revenge: Joshua Chevez went to the party intending to kill a man he believed had shot his friend but did not find that person and instead opened fire. Reluctance by many eyewitnesses complicated the investigation, but authorities identified three people they held responsible. Chevez was arrested and later convicted of second-degree murder; Jeremiah Torres was also tried and convicted of second-degree murder. A third defendant, Juan Castillo, was acquitted of murder but convicted of witness intimidation for threatening a witness.

Did anyone at the Stadium Housing Project that night know Mark or see what happened leading up to the shooting?