|The following information has been detailed in official Konami-licensed media, written by various external authors. Its status in the Metal Gear canon is unconfirmed.[?]|
The assassin managed to cross treacherous terrain without a vehicle, evade the surveillance cameras before cutting the security system's power, silence one of Miller's huskies mid-howl, and then leak sevoflurane gas into Miller's home. Miller prepared himself to attack the intruder, but was outsmarted by the poison gas, succumbing to it despite his best attempts to escape.
Behind the scenes
The assassin is indirectly mentioned in Metal Gear Solid, but is not identified. Given Liquid's later impersonation of Miller, it is implied that he was involved in the hit.
In the Raymond Benson novelization of Metal Gear Solid, the killer's method of assassination is elaborated on in the third chapter. Miller's comment about the assassin having similar skills to Solid Snake in order to pull it off implies that Liquid might have been the one who was responsible. This is further supported by Snake accusing Liquid of killing Miller. In the original game and The Twin Snakes, he simply demanded to know why Liquid disguised himself as Miller. However, the second ending timeline of Metal Gear Solid: Peace Walker refers to the assassin as an "unknown assailant", suggesting that Liquid may have simply ordered the hit.
The post-ending credits sequence of Metal Gear Solid V: The Phantom Pain implies that the assassin was none other than Revolver Ocelot, as he had predicted that one of them would eventually have to kill the other as he and Miller prepared the sons of Big Boss for the battles ahead.