The CIA's Miami office did not believe Oswald acted alone
Its officers quietly pursued Cuban exiles as suspects, and the findings were kept from investigators and remain secret.

Who Killed JFK? · Withheld Documents [BONUS]In Miami, the CIA officers who knew Cuban exiles best heard the official verdict forming in Washington, that one man alone had killed President John F. Kennedy, and did not believe it.
While leaders in Washington, along with federal investigators, officers in Dallas, and the Secret Service, described it as the act of a single gunman, the agency's Miami office dismissed that account and started its own investigation. According to Jefferson Morley, a researcher who has studied the assassination files for years, its officers opened a secret inquiry into anti-Castro exiles, whom Morley called "the people who hated him the most," to see if they had played a role.
The people closest to the exiles were pursuing the opposite theory from everyone else. Morley described it as the alternative hypothesis "that Kennedy had been killed by his enemies who were trying to lay the blame on Cuba." The suspects that the Miami inquiry examined were those anti-Castro exiles.
Morley said they "did not believe the lone gunman theory, not for a second."
What became of those findings is the other half of the story. The findings of the Miami inquiry were kept from the Warren Commission, the panel charged with finding the truth about the assassination, and remain secret to this day.
Questions people ask
What was the CIA station in Miami?
It was the CIA's large operational base in Florida in the early 1960s, known by the code name JM/WAVE. From there the agency worked with Cuban exiles on covert operations aimed at Fidel Castro's government after the 1959 Cuban revolution.
What was the Warren Commission?
It was the official panel, chaired by Chief Justice Earl Warren, that investigated Kennedy's killing in 1963 and 1964. It concluded that Lee Harvey Oswald acted alone, a finding the Miami station privately rejected.
Who were the anti-Castro exiles?
They were Cubans who fled after Fidel Castro took power in 1959, many of whom settled in Florida. Many trained with U.S. support for operations against Castro, including the failed 1961 Bay of Pigs invasion, and some blamed Kennedy after that operation failed.