WASHINGTON (AP) — U.S. Attorney General Eric Holder has ordered a federal autopsy in the Missouri shooting case of Ferguson teen Michael Brown, citing “extraordinary circumstances.”

The family’s attorney, Ben Crump, told The Associated Press that funeral arrangements for 18-year-old Michael Brown are on hold until a second autopsy can be performed.

Crump said he was in the process Thursday of making a formal request to the Justice Department. He says a second autopsy overseen by the federal agency would better ensure objectivity.

The St. Louis County Medical Examiner’s office performed a preliminary autopsy Sunday. Brown was killed Saturday in Ferguson, sparking racial tension and protests in the St. Louis suburb, including some that have turned violent.

Crump says the hope is that Brown’s funeral will take place by the weekend of Aug. 23.