Oswald had been seen on the sixth floor about 35 minutes before the motorcade passed the building. He had also been seen in the second-floor lunchroom about two minutes after the shooting. Police investigators had released him and Oswald left the building through the front door.

At 1:18, a call came in on the police radio that Dallas Patrolman J.D. Tippit had been shot at Tenth and Patton in the Oak Cliff section of town. Oswald was seen a few minutes later at the Hardy Shoe Store a few blocks away from the Tippit shooting. The witness, Johnny Brewer, led police to the Texas Theater where Oswald was arrested at 1:50. He was linked to both the Kennedy assassination and to the Tippit murder.

On November 24, as Oswald was being transferred from the City Jail to the County Jail, he was shot and killed by Jack Ruby, a local night club owner. (Ruby was convicted and sentenced to death in March 1964, but the verdict was overturned in the fall of 1966. While awaiting a second trial, Ruby died of cancer at Parkland Hospital in January 1967.)

On November 29, 1963, President Johnson established a commission, headed by Supreme Court Justice Earl Warren, to investigate the assassination. The Warren Commission made its findings public on September 24, 1964—it concluded that Oswald acted alone when he killed the President. Discrepancies in the Warren Report led to numerous subsequent official and unofficial investigations in succeeding years.

On January 2, 1979, the House of Representative's Select Committee on Assassinations supported the Warren panel's conclusion that Oswald fired the fatal shots. But, the committee also found that, based on audio recordings of the shooting taken from police radios at the time of the assassination, that a second gunman had fired at the motorcade from the grassy knoll. The House Select Committee concluded that President Kennedy "was probably assassinated as a result of a conspiracy."

These findings were later repudiated by the FBI, and in 1988 the Justice Department formally closed the investigation into the assassination, concluding that there was no "persuasive evidence" of conspiracy.