The first official investigation of the assassination was established by President Johnson on November 29, 1963, a week after the assassination. The commission was headed by Earl Warren, Chief Justice of the United States and became universally (but unofficially) known as the Warren Commission.
In late September 1964, after a 10-month investigation, the Warren Commission Report was published. The Commission concluded that it could not find any persuasive evidence of a domestic or foreign conspiracy involving any other person(s), group(s), or country(ies). The Commission found that Lee Harvey Oswald acted alone in the murder of Kennedy, and thatJack Ruby acted alone in the murder of Oswald. The theory that Oswald acted alone is informally called the Lone gunman theory. The commission also concluded that only three bullets were fired during the assassination and that Lee Harvey Oswald fired all three bullets from the Texas School Book Depository behind the motorcade. The Commission also laid out several scenarios concerning the timing of the shots, but that the three shots were fired in a time period ranging from approximately 4.8 to in excess of 7 seconds.
Fifteen years after the Warren Commission issued its report, a congressional committee named the United States House Select Committee on Assassinations (HSCA) reviewed the Warren Commission report and the underlying FBI report on which the Commission heavily relied. The Committee criticized the performance of both the Warren Commission and the FBI for failing to investigate whether other people conspired with Oswald to murder President Kennedy.The Committee Report concluded that:
"[T]he FBI's investigation of whether there had been a conspiracy in President Kennedy's assassination was seriously flawed. The conspiracy aspects of the investigation were characterized by a limited approach and an inadequate application and use of available resource." (footnote 12)
The Committee found the Warren Commission's investigation equally flawed: "[T]he subject that should have received the Commission's most probing analysis — whether Oswald acted in concert with or on behalf of unidentified co-conspirators the Commission's performance, in the view of the committee, was in fact flawed." (footnote 13)
The Committee believed another primary cause of the Warren Commission's failure to adequately probe and analyze whether or not Oswald acted alone arose out of the lack of cooperation by the CIA. Finally, the Committee found that the Warren Commission inadequately investigated for a conspiracy because of: "[T]ime pressures and the desire of national leaders to allay public fears of a conspiracy."
The committee concluded that Lee Harvey Oswald fired three shots at President John F. Kennedy. The second and third shots he fired struck the President. The third shot he fired killed him. The HSCA agreed with the single bullet theory but concluded that it occurred at a time during the assassination that differed from what the Warren Commission had theorized. Their theory, based primarily on Dictabelt evidence, was that President Kennedy was assassinated probably as a result of a conspiracy. They proposed that four shots had been fired during the assassination; Oswald fired the first, second, and fourth bullets, and that (based on the acoustic evidence) there was a high probability that an unnamed second assassin fired the third bullet, but missed, from President Kennedy's right front, from a location concealed behind the grassy knoll picket fence.
Many years after the House Select Committee on Assassinations issued its report, the attorney G. Robert Blakey for the House Select Committee on Assassinations issued a statement to the news media calling into question the honesty of the CIA in its dealings with the Committee and the accuracy of the information given to it