Bahrain's security forces continued a brutal crackdown on protesters Friday, opening fire on a march to mourn demonstrators killed earlier this week. The attack was immediately followed by a helicopter attack on journalists filming the violence, The New York Times' Michael Slackman and Mark Landler report. The military, not police, is apparently behind the crackdown, and reports indicate that live ammunition (instead of rubber bullets) are being used.

On Thursday, security forces raided Pearl Square as protesters were sleeping. Five people were killed, and riot police went after medical workers and blocked ambulances from entering the area. The opposition has withdrawn from Bahrain's parliament and is calling for the government to step down. The Daily Mirror's Greig Box-Turnbull reports that 231 were injured by live ammunition and non-lethal weapons like rubber bullets, including a five-year-old girl. Al Jazeera is also reporting that live bullets are being used.

CNN's Fareed Zarakia explains that Arab governments can be divided into two categories: "There are those that use mass repression, and there are those that use mass bribery. The mass repression is of course the Syrias of the world, and the bribery tends to be done more by the Gulf States. Kuwait and Bahrain in recent weeks have given bonuses to every citizen -- Kuwait gave $3,000 and Bahrain $2,700." But with the fall of Hosni Mubarak in Egypt, it will be more difficult to buy off the opposition in these countries. Across the Middle East, Zakaria says, "I think you're going to see an effect and a demand for accountability, for transparency, for better treatment."

Bahrain's crackdown puts the U.S. in a difficult position: it's home to a huge U.S. naval base and is crucial for launching American military efforts in the area.