Oscar McDonnell was the scientist in charge of the Care Labs, a government-owned project developing new weaponry. He was responsible for the creation of Cyborg X. When the cyborg brought Oscar an injured Spider-Man, Oscar took care of the fallen hero. He put the left arm of Spidey in a special cast which allowed the hero to have full function in the injured limb while said limb healed at an accelerated pace. He helped Spidey maintain his secret identity while injured.
Care Labs was then attacked by the incomplete Sinister Six (Dr. Octopus, Electro, Hobgoblin, Mysterio, Vulture). 47 people were killed in the attack, 162 were wounded. As Oscar was not seen afterwards, he can be presumed among the casualties.