Lurking within the confines of an abandoned hospital the PTSD-stricken veteran dons a welder's mask and equips himself with a variety of power-tools by which to hunt down and massacre any who dare stray into his path : at the same time a group of hormone-driven teens decide to use the hospital as a place to play a game of paintball, as well as engage in wanton sex.
This inevitably results in Hazard Jack going on a particularly brutal rampage, ending in the death of several of the group and the apparent death of Jack himself when the survivors manage to knock him into a vat of explosive gas, which ignites due to the sparks of his powersaw and engulfs the murderer in a cloud of flame.
Jack's trademark weapons are a large axe, a hand-held drill and a small power-saw as well as a room filled with torture devices - he also made use of a staple gun and even a flamethrower but by far his favored weapon was the axe (followed closely by his power-saw) : he also wore a welder's mask to hide his identity and the mask was caked in dried blood, along with the rest of his outfit, the result of a man who was too emotionally unbalanced to even clean himself after his rampages.
Due to his emotional imbalance Jack was not a subtle killer, indeed instead of striking from the shadows he would outright run after his enemies and fearlessly cut down anyone or thing - unlike most killers in horror Jack did not always torture his victims, in fact many died rather quick : though he did seem to prefer to torture women over men (who he killed rather quickly in comparison).
This is shown in how Jack would kidnap and strap women to his torture devices whilst granting the men a near-instant death (such as beheading or a nail to the skull) : it is unlikely this had any misogynist tones however, as Jack was not specifically shown to hate women.