On April 10, 1963, Oswald shot and missed a target he’d been stalking for weeks: The conservative and anti-communist former U.S. Army General Edwin Walker. The failed shot was fired from the same Mannlicher-Carcano rifle Oswald would use to kill JFK just seven months later.

Texas Governor John Connally was seated in the passenger seat directly in front of Kennedy when the president was fatally shot. Connally survived wounds to his chest, lungs, back and thigh. Another survivor was bystander James Tague, a local car salesman whose cheek was struck after a shot meant for Kennedy hit the curb and sent debris flying.

Dallas police offer J. D. Tippitt was not so lucky. After confronting suspect Oswald around 1:15 P.M., Oswald opened fire and shot Tippitt multiple times with a revolver, killing him instantly.

Vice President Lyndon B. Johnson and his wife, Claudia “Lady Bird” Johnson, were riding in the motorcade two cars behind Kennedy when the president was shot at 12:30 p.m. They sped toward Parkland Memorial Hospital, where Kennedy was pronounced dead at 1 p.m. From there, the Johnsons, along with First Lady Jackie Kennedy, a security detail, and the body of the slain president, went aboard Air Force One, where Johnson was sworn in as the 36th president of the United States.

Nightclub owner Jack Ruby shot and killed Oswald on live television two days after JFK’s assassination. Carrying a concealed pistol, Ruby joined crowds of onlookers and cameramen while Oswald was being transferred from the city jail to the country jail. The public execution sparked rumors that Ruby murdered Oswald to stop him from revealing a larger conspiracy at trial. Ruby claimed he killed Oswald so Kennedy’s widow, Jackie, would not have to return to Dallas for the trail. Ruby was initially sentenced to death for murder, but his sentence was overturned. He died before his second trial could take place.

One week after the shooting, President Johnson convened the Warren Commission, led by Chief Justice Earl Warren, to investigate Kennedy’s assassination. After 10 months, the committee concluded there was “no evidence that either Lee Harvey Oswald or Jack Ruby was part of any conspiracy, domestic or foreign, to assassinate President Kennedy.” It failed to silence rumors that Oswald did not act alone: “It was a terrifying thought that this little man with a $21 mail order rifle could bring down the most powerful man on earth,” says Philip Shenon, author of A Cruel and Shocking Act: The Secret History of the Kennedy Assassination.

In the 1970s, two investigations into the activities of U.S. intelligence agencies—The Rockefeller Commission and The Church Committee—essentially agreed with the Warren Commission’s findings. Over a decade after Kennedy was shot, The House Select Committee on Assassinations re-examined the evidence. In 1978, it concluded that Kennedy was “probably assassinated as a result of a conspiracy,” though “the committee is unable to identify the other gunman or the extent of the conspiracy.”

Committee members later distanced themselves from the findings. “Their conclusions were based on disputed acoustic evidence that didn’t hold up,” says Shenon, referring to analysis of gunshot recordings from Dallas police radios that led the committee to believe that there were two different shooters that day.

Lee Harvey Oswald defected to the Soviet Union in 1959 before returning with his Soviet-born wife, Marina, to the United States in 1962. The CIA was monitoring Oswald on his September 1963 trip to Mexico City—a mere month before the shooting. While in Mexico, Oswald visited the Soviet and Cuban embassies and even voiced plans to kill Kennedy. The CIA downplayed their knowledge of Oswald’s travels to the Warren Commission.

“They lied outright to the Warren Commission,” says Shenon. “The whole cover story from the CIA and FBI after the assassination was that Oswald was this lone wolf who could never have been foreseen as a threat before the assassination. The truth is the FBI and CIA were closely surveilling Oswald in the weeks and months before the assassination. Both agencies were terrified that their failure to subdue Oswald would be revealed publicly and they missed evidence that could have allowed them to preempt Kennedy’s murder.”

Just days before assassinating Kennedy, Oswald visited the FBI’s Dallas office and left a note threatening agent James P. Hosty, who had been making inquiries about Oswald and his Soviet-born wife, Marina. Hosty was ordered to destroy Oswald’s letter by his superiors, and Hosty’s name was removed from a key piece of evidence presented to the committee: A typed copy of Oswald’s personal address book. “The FBI had that note destroyed because it would prove the FBI was well aware Oswald was threatening violence right before the assassination and was a dangerous character they should have rounded up before Kennedy entered Dallas,” Shenon says.

In a memo written two days after the president’s death, then-F.B.I. Director J. Edgar Hoover wrote: “The thing I am concerned about…is having something issued so we can convince the public that Oswald is the real assassin."

“J. Edgar Hoover and the Agency were one and the same,” says Shenon. “The legacy of the FBI and his own personal legacy was on the line if it were revealed to the public how the FBI had bungled surveillance before JFK’s assassination.”

Hoover may have had a secondary motive for convincing the public that Oswald acted alone: “There were very legitimate concerns in the hours after the assassination that if this was something tied to the Soviets or Cuba, the country was on the road to war,” Shenon says.

Warren Commission lawyer William Coleman interviewed Cuban leader Fidel Castro on a fishing boat off the coast of Cuba about JFK’s assassination. Over three hours of talks, the Cuban leader denied any involvement in the president’s murder. Only Warren and one other investigator were notified of the secret interview.

The CIA was withholding their own secrets about Castro from the Warren Commission: The CIA’s multiple attempts on his life. “The CIA had been attempting for years to assassinate Castro. Some of the plots involved cooperation between the CIA and mafia. It would have been devastating for the agency if it became known that they planned to harm foreign leaders and got involved with the mafia to do it,” says Shenon.

President Kennedy’s death has continued to spark discussion and conspiracy theories. Public outcry led to Congress passing the 1993 President John F. Kennedy Assassination Records Collection Act, which mandates that all government offices identify, review, process and transfer all assassination records to the National Archives and Records Administration (NARA).