The private detective agency that employed accused Denver protest shooter Matthew Dolloff is older than the FBI, was the inspiration for the term “private eye” and is credited with once saving Abraham Lincoln’s life.

While the Pinkerton agency is no house-hold name, it reentered the national consciousness on Saturday when one of the agency’s guards allegedly shot and killed a right-wing protestor in a Denver, Colorado rally.

The Pinkerton National Detective Agency was founded in 1850 by Allan Pinkerton, an abolitionist Scottish immigrant who arrived in the US just eight years earlier, the agency said on its website.

Pinkerton’s agents gathered intelligence for the Union Army during the Civil War and later helped foiled a plot to kill Abraham Lincoln, the New Republic said in a 2018 report.

During the late 19th Century the Pinkertons evolved into a for-hire company of labor union busters, earning a reputation for thuggish tactics while putting down the Ludlow, Colorado, miners’ strike, the Homestead Battle, and the Coeur d’Alene strike in 1898, the magazine said.

The agency also featured prominently in the Wild West outlaw days, and once reportedly faced off against Jesse James, the New York Times said in a report on the Pinkertons’ exploits last year.

An unblinking eye used as an agency logo inspired the term “private eye,” according to History.com.

In 1920, they were called in to help investigate the bloody Wall Street bombing that rocked the Big Apple’s financial district.

In more recent years Pinkerton detectives have been largely worked as guards for hire with a lingering reputation of doing what it takes.

News9-TV in Denver said it hired the agency guard accused of shooting dead counter-protester Lee Keltner on Saturday, said in a report that “it has been the practice of 9News for a number of months to contracted private security to accompany staff at protests.”

The Pinkerton agency did not respond to a request for comment.