11:28 crashes truck
11:32 first shot?
11:33 enters school
11:33 first shots inside school
11:36 cops enter school
11:36 two cops proceed to scene of shooting, shooting stops
11:36 shooting resumes, cops retreat but remain in the building
11:52 ballistic shield arrives
11:56 identifiable sheriff deputy arrives
12:04 second ballistic shield arrives
12:10 second ballistic shield moved aside
12:21 for the first time since their retreat at 11:36, cops move toward the classroom where the shooting occurred
12:46 cops obviously prepare to do something
12:50 the cops do something, for the first time since entering the building 74 minutes earlier
12:50 video ends