Cairo Massacre: What happened in the mosque shooting that left 50 people dead, 500 injured?

What happened in the mosque shooting that left 50 people dead, 500 injured?

First-hand account from two witnesses of the massacre in Egypt:

Six hours ago: Gun fire and people running were heard with soldiers and MOI running. MOI starting to fear tear gas at the sit-in while the Muslim Brothers shot back with birdshot. Then the APCs arrived, and Muslim Brothers took refuge in a mosque and fired birdshot from the mosque at the approaching MOI & army. The eyewitness lives on the 14th floor so she could see the entire street. But the bullets whizzed so close to the balcony she couldn’t go out the balcony and take pictures. Muslim Brothers were still shooting birdshot from inside the mosque; and fire started inside the mosque. The army didn’t enter the mosque but blocked it all round. Then the army/MOI started arresting some MB members. MB shoot birdshot from atop the mosque and from a nearby building under construction. Ambulances arrived and entered mosque, taking the injured people away. Eyewitness says some people had finished prayers and were leaving, saw MOI/army come and started to run away. Some MB members were arrested, people inside the mosque called upon them to be patient for they are heroes. Residents went down to check what happened. Army/MOI yelled at them, asked them to go back upstairs. MB chant from inside mosque at the army, “Could you do this if this was a church?’ Eyewitness says MOI/army came to clear the sit in, fired teargas, other side shot birdshot then it all spiralled out of control.

Another eyewitness is @soltanlife. @soltanlifewas at the mosque praying Fajr when it all began. According to @soltanlife(who was at the mosque) shooting started while some were still praying. Pictures posted by @soltanlifeare very graphic and live gunfire. Aftermath, empty cases of birdshot, teargas, and live bullets, pictures by eyewitness @soltanlife: http://bit.ly/13EJQQC 

So from the two accounts we understand that as the fajr prayers going on, MOI/army arrived to clear the sit-in. It seems that the MOI/army started with teargas/birdshot right after prayers, when some people hadn’t finished yet. Someone on the MB side started shooting back (birdshot), things escalated and MOI/army used birdshot, teargas, and live gunfire. Later pictures show dead MB are shot with live gunfire, some in the head or face. MB end up holding up inside the mosque, army/MOI stand outside, birdshot gunfire is exchanged still. Aftermath: 35-40 MB killed, one army/MOI officer killed, hundreds of MB arrested, more than 500 injured.