Begins with the Tuesday manifest.

Characterized by containing gameplay of the player teleporting and rapidly flying around a map, aiming at an object of interest with machine-like precision, affecting elements within the game such as deleting objects and killing NPCs. It's clear that these are not human players in these demos. Anomidae describes the movement akin to using tools like Source Filmmaker or Hammer.

The player in these demos will often automatically lock their camera onto moving objects and delete them. In the case that the moving object is not deleted (sometimes caused by the player seemingly accidentally mistaking an moving texture for an object) the player will sometimes start spamming deletion sounds while the camera flickers in place.

Extremely common starting with the tuesday manifest

Anomi says similar to the hammer editor, or SFM

#theory This can't be Umbrella Man behavior. Has different noises, different behavior. Type 6s do remote deletion, UMs do Model Mutilation

#theory This is some kind of machine learning identification system. Look how mad it gets at kleiner: https://gaq9.com/demos?demo=ep2_data49

Typical entity deletions

POV of the blue scout from eida

Unfortunately this demo just captures the blue scout. Inspecting the demo shows no other player activity to examine and navigating to the umbrella man spot shows nothing there either.

gravelgrave

Deletes an NPC, then starts a void trip by modifying noclipspeed.
Floting point issues on viewmodel