The FBI said in the statement, issued in conjunction with the Virginia State Police and the National Park Service, the 25-year-old soldier had been sought by authorities in relation to an attack on a fellow soldier at Virginia's Fort Eustis, The (Norfolk, Va.) Virginian-Pilot said.
Army officials said Spc. Mitchell Stone identified Lanum as the individual who attacked him Sunday, leaving him in stable condition with wounds to his neck.
Lanum, who served in Iraq for 18 months, then fled the base and was stopped hours later in Warren County, Va., authorities allege.
When law enforcement personnel attempted to have Lanum exit a minivan in Shenandoah National Park, they allegedly saw the soldier brandishing a gun and shots were fired.
Authorities wouldn't confirm who fired first in the incident, which ended with Lanum shot to death, the Virginian-Pilot said.