Here's a video about trying to defend against a committed attacker with a knife. This has the feel of a real attack and it's terrifying. Defending against this, especially backed up to a wall, is impossible.
Look at it the other way. If the guy in the red jacket had a gun and was trying to shoot everyone in the room, how far would he get against committed defenders with pocket knives? Fists? Knees and elbows?