Aliens? Lol.
Some members of the government and influential people have worked together secretly before to achieve their own ends.
Conspiracies do happen.
In this case there are no glaring facts needing such explanations.
Coincidences happen too.
Now, if the gunman had shot both men, proceeded through the house until he found her in the basement, killed her and then left the scene and the lawyer's body was found away where it was later, that would seem more open to dual likelihoods.
As it stands, a pro hitman sent to kill her would not have shot the men at the entrance and run away without completing the job. And, alternatively, if the hitman was sent to kill her family members and not her (banana republic style of sending a message), then how would the gunman know she wouldn't have been first to answer the door?
No, I don't at all believe this one was a planned cover up. But, sigh, it reminds me of others.