The first day or two of the Egyptian military’s overthrow of President Mohammed Morsi’s regime went relatively smoothly, but violence mounted through the weekend, including a horrifying attack in which Muslim Brotherhood supporters threw three teenagers off the roof of a building in Alexandria, killing one of them.

Monday brought the bloodiest encounter yet, as military forces fired upon Muslim Brotherhood demonstrators outside the barracks in Cairo where the deposed President Morsi is being held. According to the Associated Press, at least 42 people were killed, plus 320 wounded. Fox News has sources who “described seeing Muslim Brotherhood supporters with large chest wounds and fatal gunshot wounds in their backs.”

Morsi supporters portray this as an unprovoked attack by the military while the protesters were conducting their morning prayers. Military authorities say they were responding to an organized terrorist attack on the barracks, as related by Fox News:

Military spokesman Col. Ahmed Mohammed Ali said initial information indicates that gunmen affiliated with the Brotherhood tried to storm the Republican Guard building shortly after dawn, firing live ammunition and throwing firebombs from a nearby mosque and rooftops. One police officer on the scene was killed, he said. Another military spokesman, who declined to be named because he was not authorized to brief reporters, said five from the Brotherhood side were killed. A statement by the armed forces published on the state news agency said “an armed terrorist group” tried to storm the Republican Guard building, killing one officer and seriously injuring six. The statement said the forces arrested 200 attackers, armed with guns and ammunition.

Witnesses say the incident began with a shower of non-lethal ammunition from the military – including tear gas, birdshot, and rubber bullets – but then escalated to live automatic weapons fire. State-run television, currently in the hands of the military, has been broadcasting images of protesters attacking soldiers with rocks, sticks, and firebombs.

In the wake of the shooting, the Salafi al-Nour party – i.e. the even more extreme Islamists – announced a “complete withdrawal” from negotiations to form a new government. They weren’t exactly eager participants to begin with, having scuttled plans to install reformer Mohammed ElBaradei as interim prime minister – apparently just minutes before interim president Adly Mansour was to announce ElBaradei’s appointment.

For their part, the Muslim Brotherhood has been showing its support for the new government by circulating rumors that Mansour is secretly of Jewish descent, and tried to get the Coptic Pope to baptize him as a Christian. For good measure, they accused would-be prime minster Mohammed ElBaradei of objecting to Holocaust denial, an outrage that practically makes him Jewish too. The Obama Administration and its mouthpieces insist that these guys have to be part of any new Egyptian government, while pro- and anti-Morsi supporters are once again lining up for street battles today, so the revolution has its work cut out for it.