11:14 AM, April 20, 1999. "A" Lunch at Columbine High School; 488 people are in the cafeteria. A janitor turned off the cafeteria surveillance cameras to rewind the tape they recorded on, missing capturing Eric Harris and Dylan Klebold leave two duffel bags on the floor beside two different tables. The bags could be seen clearly on the tape when it resumed recording 11:22 AM. Students were beginning to notice what was happening outside; some went going to the big front windows to have a look.
At 11:24 AM Coach William "Dave" Sanders and school custodians Jon Curtis and Jay Gallatine entered the cafeteria to find out what was happening outside. Seeing the shooters and realizing the danger, they - with the help of a school security officer - directed students to get down, to hide under the tables and to get out of the cafeteria by leaving through the east exits. As students began to understand the situation was serious, many panicked and ran. They left behind their books, backpacks and some even ran out of their shoes in their haste to get to safety. After evacuating the cafeteria, Coach Sanders headed up the stairs where he would be fatally shot by the same people he was trying to protect the kids from.
The security cameras in the cafeteria were the only surveillance cameras in the portion of the school where the shooters attacked. There were no cameras in the library: Several YouTube users have posted footage clipped from the film Zero Day over the years, claiming it's actual footage from the Columbine massacre. One dead give-away (aside from the fact that it's library footage and Columbine had no cameras in the library) is the date on the bottom of the of the "surveillance footage" -- it's 2 years after the Columbine shootings, and the wrong month. The screenshots and link below are legitimate. If it's not posted here, chances are it's not real.