Five journalists killed for their views. A shadowy group  dedicated to the overthrow of a foreign government. A death squad. 

It sounds like something out of a mystery novel, but it's actually the latest investigation by ProPublica and PBS Frontline that focuses on newly-arrived Vietnamese immigrants to the U.S. in the 1980s.

The deaths of the five journalists were never solved, and no one has been brought to justice. Reporter AC Thompson has painstakingly investigated the murders, and believes he's tracked down who killed them, and why. 

He laid out the story for host A Martinez. You can read the ProPublica piece here, and watch the PBS Frontline video here. 

To listen to the full interview, click on the blue audio player above.