Hans Tiedemann was the highest civil authority present on Titan Station at the time of the Necromorph outbreak. A letter from him found later in the game lists his position as Director of Operations aboard the station.
Repeating videos of him can be seen in certain areas of the station, urging its residents to evacuate, and declaring martial law. Graffiti covered posters of him can also be seen, indicating that he was not well loved among the station's population, the Unitologist portion of it anyway.
He is Isaac Clarke's primary human antagonist throughout the game, and he utilizes numerous automated subsystems as well as teams of Security Officers to halt Isaac's progress throughout the Sprawl. There is also evidence of him being controlled by someone going by the alias Overseer. The Overseer had sent a log detailing disappointment in the station's evacuation, and promise retribution against Tiedemann for authorizing it.
Despite his numerous attempts to kill Isaac and his heavy handed attitude, Tiedemann seems to see himself as a protector of the station's residents. In one audio log he is heard to say that his family had a long standing history as runners of the station, and that he wanted to protect the station and its population from the Necromorph infestation. This may be the reason he ordered the evacuation in an attempt to save as many people as he could from the Necromorph outbreak on the sprawl despite being ordered not to launch one. It is unknown exactly how many, if any people survived their escape from the Sprawl. Multiple shuttles are seen leaving the station in the earlier scenes of Dead Space 2, some crashing into each other but others making it out apparently unscathed. It is not known, however, if those shuttles/ships were carrying any Necromorphs or the insane.
After hampering Isaac at every turn, Isaac finally pushes into the Government sector with the help of Ellie. Isaac unleashes the Necromorphs upon all of his security personnel to finally confront him in front of the new, 100 story tall Marker. At this point Tiedemann has sustained horrific wounds from an earlier explosion, caused by the Marker, which has left him badly burned down his right side to the point that his skull and muscle tissue is showing.Shouting at Isaac in rage and impaling him with several Javelin spears he says that "The research in that Marker is worth every life we just lost! I won't let you throw all this away". Isaac, however, gains the upper hand and breaks Tiedemann's arm and impales him in the neck with his own Javelin Gun. Isaac can then choose to execute him with a shot to the back of the head which completely decapitates him, or electrocute him, shoot him anywhere else in the body or leave him to die from his neck wound.