Hackers have stolen and pubilshed online 300 GB of data from law firm Puckett & Faraj which represents a US Marine accused of killing 24 Iraqi civilians in 2005.
Staff Sgt. Frank Wuterich received no jail time last month in a sentencing that followed a deal in which he pleaded guilty to negligent dereliction of duty.
He initially faced up to 152 years in prison for nine manslaughter charges stemming from a raid on homes in the Euphrates Valley city of Haditha.
Wuterich admitted to telling his men to "shoot first, ask questions later," which they did, killing seven children, three women and a 76-year-old man, according to reports.
The plea bargain approved by Lt. Gen. Thomas Waldhauser called for no jail time but he not explain why he offered the deal, reports said. The sentencing judge recommended Wuterich's rank be reduced to private, which came with a moderate pay cut.
Anonymous stole court mails, faxes and transcriptions from Wuterich's lawyers and sought volunteers to help build a search engine to sift through the data.
The group tweeted it was angry military prosecutors were aggressively pursuing accused WikiLeaks source Bradley Manning, but had let Wuterich off easily.