|The following is based on the official Fallout 3 editor tutorial and has not been confirmed by canon sources.|
Very little is known about the Vault 74 Overseer. Dialogue from him is only mentioned once, inside the Vault 74 Overseer's Log, as shown below:
Data Log #10.44.78
The Vault has been breached.
There was not enough power to level Five!
God have mercy on our souls.
The Vault 74 Overseer was most likely killed by raiders when they raided and destroyed most of Vault 74.
The Vault 74 Overseer is mentioned only in the tutorial of the G.E.C.K.