When the head of the agency concerned receives information that he considers to conclusively establish the death of an employee, he shall take action thereon as an official report of death, notwithstanding an earlier action relating to death or other status of the employee. After the end of 12 months in a missing status prescribed by section 5565 of this title , the head of the agency concerned or his designee shall make a finding of death when he considers that the information received, or a lapse of time without information, establishes a reasonable presumption that an employee in a missing status is dead.