When the shooting started, school janitor Rick Thorne ran through the school warning teachers to close their doors and then used a master key to lock many of the doors for them. The state police SWAT team that was clearing the school after the shooting had to get the key from Thorne to open some of the rooms. The key was so worn from use that morning it snapped in one of the doors.
A source with knowledge of the probe said that when Lanza drove to the Sandy Hook Elementary School he parked his car in a way that could have set him up to ambush responding police officers. He parked with the passenger's side facing a small brick wall near the front entrance. His shotgun was left leaning against the passenger's side door.
The spot gave him potentially a perfect line of sight to shoot at unsuspecting police driving down the long driveway, around a curve and into his line of fire. It also provided him cover since the school and woods were behind him.