The dense snow and blizzard-like conditions outside the Massachusetts home are gone. But the mystery of who may have killed Boston Police Officer John O’Keefe on a frigid night in Canton lingers as jurors visited the house near where his body was found.

Karen Read pleaded not guilty to murder charges in the death of Boston police officer John O’Keefe and is facing a retrial after a jury was unable to reach a verdict last year.

A Canton firefighter testified Friday that Karen Read told him she was upset because her final conversation with John O'Keefe was an argument. Friday's proceedings ended for the day shortly after 1 p.