Traffic cops stopped the Bundy brothers and seven others on Tuesday
Shots were fired, Ryan Bundy was wounded, a militiaman was killed
Ammon Bundy and three others were detained at the scene, they have been charged with 'conspiracy to impede federal officers'
Not clear who opened fire; the hospital and highway are on lockdown
It comes more than three weeks after the Bundy brothers led an occupation of a federal building in Burns, Oregon, to protest 2 ranchers being jailed