“A black bloc is a tactic for protests and marches where individuals wear black clothing, scarves, ski masks, motorcycle helmets with padding, or other face-concealing items.[1][2] The clothing is used to conceal marchers’ identities, allow them to appear as one large unified mass, and promote solidarity.”
“Tactics of a black bloc can include offensive measures such as street fighting, vandalism of corporate property, rioting, and demonstrating without a permit, but mainly consists of defensive tactics like misleading the authorities, assisting in the escape of people arrested by the police (”un-arrests’ or “de-arrests”), administering first aid to persons affected by tear gas, rubber bullets and other riot control measures in areas where protesters are barred from entering, building barricades, resisting the police, and practicing jail solidarity.[25][26][27] Property destruction carried out by black blocs tends to have symbolic significance: common targets include banks, institutional buildings, outlets for multinational corporations, gasoline stations, and video-surveillance cameras.[28]”
http://en.wikipedia.org/wiki/Black_bloc
"Occupy Oakland Embraces Nonviolence, but Debates 'Black Bloc' Tactics"
http://www.time.com/time/nation/article/0,8599,2098891,00.html
For what its worth...
“UPDATED: Is James E. Holmes A Occupy Black Bloc Member
He Plotted to Kill Cops
James E. Holmes Shoots Up Aurora Co Movie Theater Killing 12 And Wounding 59 As Batman Movie Slams OWS”:
http://cheatersflorida.wordpress.com/2012/07/20/updated-is-james-e-holmes-a-occupy-black-bloc-member-he-plotted-to-kill-cops-james-e-holmes-shoots-up-aurora-co-movie-theater-killing-12-and-wounding-59-as-batman-movie-slams-ows/
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“More Signs Point to James E. Holmes As Occupy ‘Black Bloc’ Member He Plotted to Kill Cops With Firebombs Just Like Black Bloc Chicago”: