I… For Icarus(1979)

Just as Henri Volney (Yves Montand) is nearly ready to blow the conspiracy wide open, accusing several members of the secret police of conspiracy in the murder of President Jarry, he shot dead in his office by a sniper, obviously on orders of the cabal that arranged the President’s murder as he had gotten too close to the truth.

The implication is that the remaining conspirators will ransack his office and steal the evidence he had gathered, leaving his team with no other avenue but to close the case lest they be targeted and killed next.