The death of former White House press secretary James Brady, who was shot in the head in the 1981 assassination attempt on President Ronald Reagan, has been ruled a murder.
John Hinckley Jr shot Mr Brady, who never regained normal use of his limbs and was often in a wheelchair.
His family said he died on Monday aged 73 from a series of health issues.
After the shooting, Mr Brady undertook a high-profile, personal crusade for gun control, which continues to be one of the most hotly debated issues in the US.
The Brady law, named after him, requires a five-day wait and background check before a handgun can be sold. President Bill Clinton signed it into law in 1993.
A post-mortem revealed the cause of death to be a gunshot wound and its health consequences, and the manner of death was ruled a murder, according to District of Columbia police. The Virginia medical examiner's office made the ruling.
Hinckley attempted to assassinate Mr Reagan outside the Washington Hilton Hotel on March 30, 1981, just two months into the new president's term.
Mr Reagan nearly died from a chest wound. Three others, including Mr Brady, were struck by bullets from Hinckley's handgun.
Hinckley, now 59, was found not guilty by reason of insanity of all charges in a 13-count indictment, including counts of attempted assassination of the president of the US, assault on a federal officer, and use of a firearm in the commission of a federal offence.
William Miller, a spokesman for the US attorney's office in Washington, said the office "is reviewing the ruling on the death of Mr Brady and has no further comment at this time".
Gail Hoffman, a spokeswoman for Mr Brady's family, said the ruling "is not a surprise to any of us".
She said the family would respect whatever prosecutors think is appropriate in dealing with the ruling.
Tung Yin, a professor of law at Lewis & Clark Law School in Portland, Oregon, said that it is rare that the act that could be considered the cause of a murder occurred so long ago.
"It seems a little bit unprecedented," he said of the Virginia medical examiner's ruling. He said such cases more usually involve a person in a coma who dies a year later.
He said bringing such a case could cause problems for prosecutors, because Hinckley was found was found not guilty by reason of insanity.
"A jury has already concluded on the same incident that he (Hinckley) was not guilty. Nothing today changes that," Mr Yin said, even if prosecutors say Hinckley is no longer insane.
"That doesn't change what he was 33 years ago."
Calls to Hinckley's lawyer's were not immediately returned. Barry Levine, Hinckley's long-time lawyer, has said in court hearings that Hinckley is not a danger.
Officials at St Elizabeths Hospital in Washington, where Hinckley is a patient, have said that the mental illness that led him to shoot Mr Reagan in an effort to impress actress Jodie Foster has been in remission for decades.
Hinckley has been allowed to leave the hospital to visit his mother's home in Virginia and can now spend more than half of his time outside the hospital on such visits.