I am not well versed with Gargoyles so mind giving me the canditates of who is this poor fool could be?
Foremost suspect:
Oberon - The season finale to season 2 of Gargoyles saw Xanatos calling upon friends, family, allies and enemies in an attempt to keep his son safe from Oberon, the god-like king of the fae. Xanatos was married to Fox Xanatos nee Janine Renard.
Fox was the half fae daughter of Titania, who had been living as a human after Oberon exiled her (and the rest of the fae) from their homeland of Avalon for a thousand years. During those years, Titania married with one Halcyon Renard, genius industrialist, and from that marriage Fox was born.
Titania considered that the half fae heritage in Fox had died without manifesting, but thought that her grandson (the son of Xanatos and Fox) could be nurtured even though he was only one quarter fae. This happened at the end of the thousand year exile and Oberon recalled all the fae to Avalon. He showed up at Xanatos HQ trying to track down the Puck (who was disguised as Owen Burnett, Xanatos personal assistant), found Titania and upon learning about the kid decided that he was taking him too.
Canonically, Oberon was able to eventually bulldoze through the various defenses that had been deployed against him, but he was convinced to leave the kid with the parents when Fox awakened her magic just in time to blast Oberon through a wall. Puck, who had actively attacked Oberon, was sentenced to become a human at all times, except when teaching the kid to use his magic.
The other names that potentially come to mind...
Thailog - Gargoyle clone of Goliath, with Xanatos level intellect and literally zero morals. Possibly the CEO of Nightstone Unlimited.
Demona - Crazy immortal gargoyle witch who was a partner of Xanatos, until she decided to betray him for good. Has genocidal plans against humanity (almost released a bioplague that would have wiped out humanity towards the end of Gargoyles season 2), some magical ability and keeps grudges as if she was one of the Warhammer dwarves. Also possibly the CEO of Nightstone Unlimited, whom she created along Thailog.
There may be a few other candidates, but those three are probably the foremost suspects, because the number of people actually capable of killing Fox (who was canonically an extremely capable mercenary) is not that high to begin with.