>> reporter: according to various eyewitnesses, the muslim brotherhood was holding a peaceful sit-in demonstration they have been conducting the past few days at a site where they believe morsi is being held. they say they were attacked by terrorists who tried to storm the headquarters. 51 people have been killed. more than 300 have been injured. this is the type of violence that most people here are fearful will set off a larger clash across the country. it demonstrates how deep the divisions are. very little trust between the two groups. patti ann: what effect is today's violence having on the military-backed government? >> reporter: we are seeing the divisions went pro morsi and