instructions for the protest were clearly disseminated on facebook

Instructions for the protest were clearly disseminated on Facebook: Stand 5 feet apart, so as not to break Egyptian laws against public demonstration; be absolutely silent; no signs; wear black, as determined in an online vote; stand on the banks of the river or sea for one hour only, then walk away.

No one yet knew who had organized this protest against police brutality. There were five Facebook page administrators, tech-savvy activists who didn’t really know each other.

(source)