I saw that video. If you are in a place with no easy exits and you can't carry, the video is actually a decent one.
The building that I am in is over 500 feet long with exists on both ends and a tight stairwell in the middle. The fire drills we practice have us moving to the outside stairwells which naturally get clogged up. The other week management forgot to inform anyone that they were working on the alarm system and the alarm with went off with the message "evacuate the building immediately". People freaked out bad because the message didn't explain what the threat was. People didn't know if there was a bomb, a shooter in the building, a fire...etc. People were leaving but weren't sure about going outside. As I got to the exit they started informing people it was a false alarm. Then as people were walking back they were trying to figure out what to do if it was an active shooter and where they would hide because obviously running isn't going to work since the stair wells were clogged.
Of course that got me thinking. If a shooter wanted to obtain maximum casualties they just need to pull the fire alarm from the center of the building, give it 30 seconds and then shoot everyone in the back they are running to the clogged stairwells. The building is setup like a shooting gallery with long straight corridors.