The Elevator of Blood

Spooky? Sure is, get out of here kids! Ahem, the Elevator of Blood was one of the more fierce and stunning scenes in a horror movie of the earlier times, it appeared three times in the movie... when Danny had his first vision of the blood leaving the elevator, when Jack was talking about Danny to Wendy when he was going nuts, and finally... when Wendy was running all over the hotel searching for Danny as she witnessed the elevator shoot out blood... LIKE THIS!

What actual marking did the Elevator of Blood hold? Why did it exist? To inflict fear I assume and also I assume it's all the blood that was ever spilled in the hotel.