The disturbing history of how tear gas became the weapon of choice against protesters

The chemical weapon was originally marketed to police as a way to turn protesters “into a screaming mob.”

It was a chilling split screen at the start of June: President Donald Trump preparing to give an address in the White House Rose Garden as dozens and dozens of protesters right outside were being pushed back on the streets by federal law enforcement firing what appeared to be tear gas.

Similar reports of police using tear gas against protesters have emerged across the United States over the past several days: San...