Trial began Tuesday for a man accused in the deadly shooting ambush of Baltimore police officer Keona Holley who was sitting in her patrol car when she was killed in 2021. But the case remains shrouded in mystery more than two years later as prosecutors have said nothing about a potential motive. Police quickly arrested two men who allegedly shot Holley before authorities say they committed another homicide about 90 minutes later in a different Baltimore neighborhood. One of them, 34-year-old Elliot Knox, is on trial this week. His attorney argued he wasn't the shooter and should be found guilty of accessory after the fact, not murder.