After their investigation, they concluded that the official narrative was most likely wrong and they found a high probability that two gunmen fired at President John F. Kennedy.
There were no investigations after that..
> Scientific acoustical evidence establishes a high probability that two gunmen fired at President John F. Kennedy. Other scientific evidence does not preclude the possibility of two gunmen firing at the President. Scientific evidence negates some specific conspiracy allegations.
> The committee believes, on the basis of the evidence available to it, that President John F. Kennedy was probably assassinated as a result of a conspiracy. The committee is unable to identify the other gunman or the extent of the conspiracy.
https://www.archives.gov/research/jfk/select-committee-repor...