St. Louis County Prosecutor Robert McCulloch said Saturday that a grand jury will begin hearing evidence in the Michael Brown shooting case next week.

“We are doing it as we go along” rather than wait to present entire body of evidence to grand jury, McCulloch said in a brief phone interview.

Brown was fatally shot by a Ferguson police officer a week ago.

Meanwhile, a law enforcement source confirmed Saturday that federal authorities had opposed the release of surveillance video that showed Brown stealing from a convenience store shortly before he was shot.

The Ferguson police department wanted to release the video on Thursday; Justice Department asked it not to, believing the video would roil the tense community further, and successfully prevented the video’s release at that time.

Friday’s release of the video occurred over the objection of federal authorities, the source said. A copy of the video has also been in possession of federal investigators and there were never any plans to release that copy.