Prosecutors are compiling a growing dossier on Eduardo Luna, identified as an alleged former member of the powerful Gulf Cartel.

The brother of a U.S. Border Patrol agent charged with capital murder in an alleged Mexican drug cartel hit struck a surprise deal last week to help prosecutors build their case against his siblings.

The circumstances of their crimes differ, but prosecutors say defendants in 140 cases have something in common: The corrupt actions they’re accused of weakened the U.S. borders and ports of entry they were assigned to protect.

A headless body is found in a Texas bay. The case bears the familiar markings of mafia muscle and hardball tactics associated with cartel warfare. But