Tom Corsi was a caucasian American Vietnam veteran, who worked as a policeman around the Westchester area of New York. There he enjoyed the challenges of the job and helping people in the local community.
One night during a heavy snow storm, Danielle Moonstar was rushed into the Emergency Room. She had been severely attacked, with wounds that appreared to be consistant with a bear attack. Unknown to Officer Corsi or any of the emergency staff, Dani was the New Mutant known as Psyche, and she had been attacked by the ferocious spirit known as the Demon Bear.
Officer Corsi was shocked, as there were no bears in Westchester. He patiently patrolled the corridors of the hospital, and caught something leaning up against the door of the Operating Theatre. Having never seen anything like it before, he threatened to shoot the intruder. However, what Officer Corsi didn't realise was that he had seen Wolfsbane in her transitional form. He chased her around the corner, and when he caught up she had transformed back into her normal human state. She was clearly afraid for Psyche's life, and he was deeply shocked by how he had nearly shot a little girl. He led her back to the others and wandered over to the Nurses' Station to relax his nerves.
The Demon Bear then plunged it's gigantic claws through their bodies, casting powerful spells over both of them. They were transformed from caucasians into Native American demons.
After the bear was defeated, Tom's body was freed of the evil spirit. However, although both he and Sharon were freed of the evil demons that possessed them, Magik could not restore their bodies to their former appearance. As William Lonestar later explained, the Demon Bear's first enchatment that transformed them into Native Americans was permanent. Magik's Soulsword had removed the demonic enchantments, but there were no more spells to be removed.
Being transformed into a different ethnic race meant that Tom couldn't return to work with the polcie force. His whole life had been turned upside down by the encounter with the Demon Bear. Professor Xavier sent him & Sharon to Muir Isle where Moira MacTaggert attempted to research for any possible cure and study their new abilities. However, Sharon & Tom were permanently transformed. While Sharon still seemed upset by her new body, Tom seemed happy with his new strength and reinvigorated youth.
Tom and Sharon returned to New York and went to live at Xavier's School for the Gifted where they assisted the new headmaster, Magneto. They became teaching assistants and confidants for the New Mutants in much the same way that Stevie Hunter had done. Having survived at least two life-changing and traumatic experiences threw their lives together. When they first met Tom had begun to flirt with Sharon, but they didn't pursue the relationship much further than friendship.
Corsi pumping iron
Corsi at the shooting range