Bombay Jack staked a claim on land near the path of an NCR railway, he then immediately started mining a path and blowing up storage sheds to deter people from moving into the area. When the NCR went looking for him they found that he had mined a huge area around his hideout. Before being caught he managed to kill at least 10 soldiers by shooting the mines around them.
He had supplied the powder gangers with homemade explosives, and so to keep their source, the gangers broke him out of the prison train. Though he was caught again and presumably sent back to prison, it's not known how he got out the second time.
Two weeks prior to the Prisoner's arrival, in response to some comments from Hardin, Bombay Jack flipped out and went off on his own, seizing a nearby claim and guarding it with explosives.
Defeat Bombay Jack in his Canyon: If the Prisoner follows Bombay Jack to his lair, or simply stumbles across it he will start attacking the Prisoner. This is a much tougher battle as Jack is in his element with many traps, which potentially includes the extreme measure of demolishing his lair with the Prisoner and any companions inside.
It was an explosion from one of Jack's devices that put Garcia in a coma.
If the salvagers finally attempt an attack on the Box, Jack will kill Murphy in the scramble.
He is of Mexican descent, and tends to speak Spanish when excited.
If Jack is attacked with a flamer or Molotov, he will blow up. If he is attacked with a gun, there's a chance equal to damage x5% he will blow up with the force of 3 cases of dynamite.
Jack has high Perception and a good ranged weapon, making him a good sniper. He will have laced the area with explosives, so he'll fire for a few rounds, then move, leaving the bomb in place, and keeps moving around from building to building, in pre-arranged niches.