I believe this is that incident:

US troops kill Afghan civilians
An incident described by US forces in Afghanistan as a "complex ambush" has left at least eight civilians dead.

The incident occurred on the road from the eastern city of Jalalabad to Pakistan when a suicide bomber targeted a convoy, sparking a fire fight.

US officials initially said 16 people had been killed. They did not explain the lower, revised death toll.

Thousands of local people took to the streets, accusing the Americans of deliberately firing on the civilians.
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http://news.bbc.co.uk/go/pr/fr/-/2/h...ia/6416667.stm
And then this which looks way to much like the cover-up:

Journalists: U.S. military deleted photos of attack

Afghan journalists covering the aftermath of a suicide bomb attack and shooting in eastern Afghanistan Sunday said U.S. troops deleted their photos and video and warned them not to publish or air any images of U.S. troops or a car where three Afghans were shot to death.

Afghan witnesses and gunshot victims said U.S. forces fired on civilians in cars and on foot along at least a six-mile stretch of road in Nangarhar province following a suicide attack against the Marine convoy. The U.S. military said militants also fired on American forces during the attack.
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http://www.cnn.com/2007/WORLD/asiapc....ap/index.html

U.S. military claims deletion of AP footage at attack site in Afghanistan justified

The U.S. military asserted that an American soldier was justified in erasing journalists' footage of the aftermath of a suicide bombing and shooting in Afghanistan last week, saying publication could have compromised a military investigation and led to false public conclusions.

The comments came Friday in response to an Associated Press protest that a U.S. soldier had forced two freelance journalists working for the U.S.-based news agency to delete photos and video at the scene of violence March 4 in Barikaw, eastern Afghanistan. At least eight Afghans were killed and 34 wounded.
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http://www.iht.com/articles/ap/2007/...Censorship.php