Task: Question Answering
Input (English): Passage: Jess Wade, a former member of a gang of outlaws led by Vince Hackett, was led to believe that an old flame, Tracy Winters, wanted to meet him in a seedy Mexican saloon.  Jess saw Billy Roy Hackett, Vince's younger brother, summoning Vince and the other members of the gang into the saloon, and realized he was being set up.  Jess ordered the bar patrons to leave before a shootout ensued.  Making a break for the door, Jess was stopped by Gunner, another gang member, and was forced to relinquish his gun and to go with them to their hideout in the mountains.  Vince later told him that the gang had stolen a gold-plated cannon that was used by Emperor Maximilian in his ill-fated fight against popular Mexican leader Benito Juarez.  Vince informed him that, according to a wanted poster, Jess was in the gang who stole the cannon and had sustained a neck wound as a result of being shot by one of the guards.
Ordering his men to subdue Jess on the ground, Vince used a branding iron to burn his neck.  They took his horse, leaving him stranded.  He captured a wild horse in the desert and saddle-broke it.  The gang's motive was to force a ransom from the town they stole the cannon from, but the gang also used the cannon to hold the townspeople at bay.  Only Wade can save the people from his former gang. 
Question: Where was the gang of outlaws's headquarters?
Output (English): in the mountains.