Final answer:
According to the Warren Report, Lee Harvey Oswald acted alone in assassinating John F. Kennedy in 1963. There is no evidence to support the involvement of any other individuals or groups.
Step-by-step explanation:
The Warren Report concluded that Lee Harvey Oswald acted alone in assassinating John F. Kennedy in 1963. The report found no evidence of any conspiracy or that anyone assisted Oswald in the assassination. This conclusion was reached after a thorough examination of all the evidence by the commission headed by Earl Warren, Chief Justice of the U.S. Supreme Court.