WASHINGTON (WUSA9) -- A U.S. attorney says John Hinckley, Jr. won't be charged in the death of James Brady, former White House press secretary and gun control icon.

Brady's death was ruled a homicide after his death in 2014 at age 73. Brady was shot during the attempted assassination of then-president Ronald Reagan in 1981.

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Hinckley was found not guilty by reason of insanity for the shooting that left Brady partially paralyzed. He has been a patient at St. Elizabeths Hospital in Washington and has received psychiatric treatment since his acquittal in 1982.

However, when Brady died in August 2014, a medical examiner attributed his death to the bullet that struck Brady in the head when Hinckley emptied his six-shot .22-caliber revolver in March 1981. The U.S. Attorney's Office started a review to determine whether to prosecute Hinckley for homicide.

Friday, the U.S. Attorney's Office for the District of Columbia announced that it would not pursue criminal charges against Hinckley. "The decision was made following a review of applicable law, the history of the case, and the circumstances of Mr. Brady's death, including recently finalized autopsy findings," read a press release from the U.S. Attorney's Office.

Part of the statement explaining the decision reads as follows:

"According to an autopsy report prepared by the chief medical examiner's office, and finalized on Dec. 4, 2014, the traumatic brain injury sustained by Mr. Brady created difficulty managing oral secretions and food and led to aspiration pneumonia and other chronic diseases. At the time of his death, Mr. Brady was suffering from aspiration pneumonia. The chief medical examiner thus concluded that Mr. Brady's death was determined to be "gunshot wound of head and consequences thereof."

"At his 1982 trial, the jury found Hinckley not guilty by reason of insanity of the two charges, assault with intent to kill while armed and assault with a dangerous weapon, related to the shooting of Mr. Brady. Because the jury conclusively made this finding, the government would be precluded now from arguing that Hinckley was sane at the time he shot Mr. Brady.

"Additionally, before 1987, the District of Columbia courts abided by the "year and a day rule," by which a homicide prosecution could only be brought if the victim died within a year and day of the injury causing death. At the time that Hinckley made his assassination attempt, the year-and-a-day rule was still in effect.

"In summary, any further prosecution of Hinckley premised on his March 1981 shooting of Mr. Brady would be precluded by the doctrine of collateral estoppel, which would prevent the U.S. Attorney's Office from arguing, or a court or jury from finding, that Hinckley was sane at the time Mr. Brady was shot. Thus, Hinckley would be entitled to a directed verdict that he was not guilty of the murder of Mr. Brady by reason of insanity. Furthermore, a homicide prosecution would be precluded by the common law "year-and-a-day rule," in effect at the time."