This video uploaded to YouTube by Ahmed Fathi, and linked to by the New York Times, appears to show protesters chanting “Peaceful! Peaceful!” before coming under attack by the security forces.

It is said to have taken place in the Suez Canal town of Ismailiya. The head of the Egyptian ambulance service has confirmed that four people were killed in Ismailiya today.

http://www.theguardian.com/world/middle-east-live/2013/aug/16/