A guy whose life was changed before it began
Tyrone is generally reserved to himself and those close to him. When he senses danger to such people, or even to a random person or group, instinct takes over. He took up boxing, so when he fights, he naturally uses his fists more than his feet to strike and doesn't jump or use acrobatics to dodge unless necessary. When he transforms, he still has human speech and movement, but whenever an instinctive urge comes on him to act a certain way (for example, lunging at or attacking something or someone), he has little to no control over it.
Tyrone doesn't usually have equipment, but he packs a revolver or double-barrel shotgun whenever necessary.
The whole ordeal began before Tyrone's birth. The fetus in his mother's womb was examined and the doctor found it hadn't grown at the usual pace. He diagnosed that unless something was done, the fetus would die and have to be taken stillborn. The treatment was supposed to be a recently-developed growth stimulant for such a time. His parents had never had a child before and had failed to conceive several times before, so they desperately agreed. However, the doctor was too sure he put the stimulant in a certain compartment of a test-tube rack out of his sight, so he grabbed a vile with a fox's DNA that had been vaporized and condensed into a serum. The DNA infused with his. It somehow worked, and Tyrone survived. The effects of that fateful assumption didn't come around until Tyrone was 13. During one of his classes, he noticed something black on his hand. Assuming he had spilled something on it, he went to the restroom to wash it off. Before he could even get to the sink, he saw the spot had covered his hand, and watched it consume his arm. He looked all over his body as it changed, and knew something was up. He hid from view, and his horror made him want to shout, but he couldn't. By the time his transformation was complete, he poked his head out and looked in the mirror. He saw he had become an anthropomorphic fox. He hopped back in the stall in shock. When a teacher was sent to get him, he refused to leave, unaware he was becoming human again. When the door opened, he wondered why the teacher was giving looking at him funny instead of in terror. Tyrone looked, and he was human. He found these episodes occurred at random. They could happen at any given moment, but they usually came up in a situation of high emotion. The most he can do is slow down these transformations long enough to escape, but he cannot stop or reverse them. He can revert to normal only after passage of time, which is also random. He has an inhibitor that can control these episodes, but it only has enough battery to run for an hour, so he only turns it on when a transformation begins. Nobody other than the inventor of the inhibitor knows of his secret, and his transformations have become more frequent, so it may only be a matter of time before someone finds out.