The U.S. soldier accused of providing classified files to WikiLeaks told his aunt a leaked video of a helicopter attack in Iraq that killed civilians would cause a “big splash,” she said in a statement at his court-martial on Tuesday.

Private First Class Bradley Manning’s aunt, Debra Van Alstyne, told Army investigators about his comment when they talked to her at her Potomac, Maryland, home in June 2010, after his arrest, according to a statement read into the trial record.

Manning, 25, is on trial for allegedly leaking more than 700,000 files, videos and other documents to WikiLeaks, an anti-secrecy website. The largest release of classified data in U.S. history included a gunsight video from a 2007 Apache helicopter attack in Baghdad in which civilians were killed, including two Reuters staffers.

In the statement read by prosecutor Major Ashden Fein, Van Alstyne said an investigator collected a digital camera data card that was found to contain some of the leaked Iraq battlefield reports and the Apache video.

Manning called her after his arrest in May 2010 and asked if she had watched the helicopter video, Van Alstyne said in the statement. She said he told her it would be “big news” and that it would make “a big splash in America.”

The soldier is accused of leaking the files while serving in Iraq as an intelligence analyst in 2009 and 2010. The 21 charges against him include aiding the enemy and he could face life imprisonment without parole if convicted.

Lawyers for Manning have described him as naive but well-intentioned in wanting to show the American public the reality of war in Afghanistan and Iraq.