https://www.vice.com/en_us/article/akdkva/the-pinkertons-are-still-messing-with-workers-now-for-amazon

Founded in 1850 by Allan Pinkerton, a Scottish immigrant who went on to become the first detective in the history of Chicago, the Pinkerton Detective Agency became synonymous in American life with conspiracy theories and violent clandestine activities—and with good reason. Though Pinkerton himself was one of the Union’s first spymasters during the Civil War and foiled an assassination plot on President Lincoln in 1861, he did what every ex-intelligence community type does after wars nowadays: Uses his government skills and contacts to profit in the private sector. 

In its early years the agency, something of a precursor to the infamous Blackwater mercenary outfit founded by Erik Prince that is linked to war crimes in Iraq, was at one time bigger than the U.S. Army and connected to outlandishly villainous plots that were in fact true. For example, Pinkerton agents were actually the private armies for the rich industrial titans of the Gilded Age, helping union bust and infiltrate workers groups. Even going so far as to shoot striking workers. Pinkerton agents were also alleged to have firebombed the home of the outlaw Jesse James’ mother (while James wasn’t there), blowing her arm off and killing his half-brother. Both weren’t involved in any of the ex-Confederate’s crimes.