BELLEVUE, Neb. (AP) — The mother of a Lincoln man killed by an Offutt Air Force Base guard during a police chase has filed a wrongful death lawsuit against the guard and Air Force commanders.

The federal lawsuit filed last week alleges that shooting 21-year-old Zachari Johnson amounted to excessive force. Douglas Bickal, an Air Force security contractor, shot Johnson in the chest when he crashed a car through a base entrance in June 2012.

Air Force officials have said the guard was following procedure.

The Sarpy County sheriff’s office says Johnson was driving a stolen Honda Civic when he raced north and tried to leave the base. The guard fired at the car three times.

The defendants haven’t yet responded to the allegations.