
As it is revealed in the game the Black Mesa scientists were constantly traveling back and forth from their dimension to the aliens and bringing back specimens for study, due to the fact that this was entirely dangerous to do, in threat of causing inter-dimensional rifts, or revealing this to the public, it was decided to silence the entire operation before anything could happen. G-man's motive for causing the incident is clearly an order by his 'employers' due to Black Mesa being as G-man tells Shephard 'one of the biggest embarrassments'. It's revealed by Eli Vance (another one of his employees) that he was the one who supplied Black Mesa with the Xen crystal that caused the accident, and he also re-activated the nuclear warhead that completely destroyed the facility. He then informs Shephard that there is still the matter of witnesses, which leads him to abandon Shephard in the Osprey which he has teleported to an alternate dimension, leaving him in what G-man sees as 'A state where you can do no harm, and no harm can come to you.' Black MesaG-man played a major role in the Black Mesa incident, being the one who started and ended it. However as it turns out G-man re-activated the warhead, destroying Black Mesa with an explosion big enough to be seen from the Osprey. G-man then informs Shephard that he has done good in his mission and that he has ultimately ended the second invasion. Upon the Gene worm's death Shephard wakes up inside a V-22 Osprey like the one he came to Black Mesa in, except with G-man inside. Shephard then goes on to deactivate a nuclear warhead placed by Black Op soldiers and destroy the Gene Worm, a large powerful alien coming through a portal in the basement that all the other soldiers failed to destroy. Shephard is deployed soon after to combat the incident where he loses most of his squad, and is forced to retreat with the rest of the soldiers, only to be stopped by G-man, denying him escape and forcing him to delve deeper into the facility. G-man can be seen standing in a window looking down at Shephard in the camp, emphasizing that G-man bumped him up intentionally. Shephard enters the military academy to become a simple soldier but is strangely bumped up to special training for the HECU. When he confronts Gordon at the end he offers him a job working for him and leads him through a portal which then takes off in Half life 2, but if refused he will teleport him back to the alien homeworld in front of an army of alien grunts leaving him to be massacred by what he addresses as 'survivors of your personal holocaust.' Adrian ShephardAdrian Shephard is a military operative of the Hazardous Environment Combat Unit that infiltrates the facility to combat the alien forces, and Black Mesa personnel.

Though G-man's conversational skills are calm and professional, his negotiation skills are designed to get what he wants. G-man is seen constantly watching Gordon from a distance even before the incident occurs, he is finally confronted at the end of the game explaining that his 'employers' agree with him that Gordon has limitless potential.
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G-man is very interested in Gordon, seeing him as a perfect employee due to his persistence and skills which ultimately lead him to stop the invasion and save the world. Gordon Freeman is a scientist in the Anomalous Materials Labs of the Black Mesa Research Facility where the entire incident begins.
