They don’t necessarily know what the mission was, just that the mission left dead bodies. Furthermore, they don’t know which country did it. There are probably

They don’t necessarily know what the mission was, just that the mission left dead bodies. Furthermore, they don’t know which country did it. There are probably a dozen countries that would do a mission like this against them with various objectives. You also have to consider the possibility that the mission was intentionally designed as a distraction, such that the purpose was to leave evidence of a mission.