Jay Nixon declared a "state of emergency" in Ferguson, ordering a curfew between midnight and 5:00 a.m. CDT. At about 12:45 a.m. police fired tear gas at protesters. According to accounts on Twitter, police announced that they would be arresting everyone. Cops created a "zone" for journalists to remain in. Huffington Post journalist Ryan Reilly said on Twitter that he and other reporters asked cops to allow a small group of reporters to get closer to the police action—they were, predictably, denied. The adage that "it's better to ask forgiveness than seek permission" probably applies here.
Meanwhile in a pretty depressing journalism fail, Politico's Byron Tau, also in Ferguson, explained on Twitter that the First Amendment's "subject to reasonable time and place restrictions." He can't witness police enforcing those restrictions because he's in the "first amendment zone" behind riot police, where the view is obscured.
There are also reports of shots fired from multiple observers on the ground. Reilly tweeted that police radio also mentioned a person shot, though it was unclear if it was by a rubber bullet or the traditional kind. CNN commentator Marc Lamont Hill, on the ground in Ferguson, tweeted that a "kid" was shot but not by police.
You can watch what's happening on a stationary livestream from Argus Radio here and a roving one from Vice News here. You can follow a bunch of people on Twitter, including the ones linked to above. I'll keep retweeting for a while longer so you can check my feed to find other observers to follow.
Via News2Share, here's video of some of the tear gassing: