As you go throughout your travels, you will sometimes happen upon Dex, who is a character from the first two Saints Row games. All you have to do is kill him, which is easy as his health is similar to a normal Husk's health. As you kill him, though, he will return with weapons, as well as with some help in the form of demon allies.
Dex operates on a seven-kill cycle, with his demon allies getting stronger each time, before reverting back to the beginning of the cycle. The allies begin with imps, then moves onto regular demons and culminates in two Legionnaires at the seventh appearance. Killing Dex seven times will get you the Gallows Dodger weapon.