PORTLAND, Ore. -- A federal prosecutor revealed in a court document that the investigation of FBI agents involved in the traffic stop that led to the killing of Oregon standoff spokesman Robert "LaVoy" Finicum is before a grand jury.

Attorneys for the defendants accused of taking part in the Ammon Bundy-led takeover of a national wildlife refuge in Oregon have been seeking records from the investigation into the FBI's use of force in the Finicum shooting and whether there was a cover-up.

In a motion to keep reports sealed, Assistant U.S. Attorney Charles Gorder wrote Thursday that matters before a grand jury are protected from disclosure rules.

Oregon State Police troopers fired the rounds that killed Finicum during the Jan. 26 confrontation on a remote road, and the shooting was deemed to be justified.

Investigators, however, discovered FBI agents failed to disclose they fired two rounds that missed Finicum.