Warning This Section Does Contain Spoilers
The letter from Dr. William Richter to Dr. Samuel J. Hawkins was written on 27 September 1967. This verifies that Lilian Grayson died on this date since he says "what happened in my ward today." The dates on her autopsy are double typed and hard to read.
The letter goes on to say that Lilian was found dead in the janitor's closet early in the morning. He describes her amusing and something of a jokester who put other patients at ease. And that the loss of such a "bright star is an altogether a most unfortunate event."
He puts the blame on Lloyd McGowan who is said to have broken free of his quarantine through an unlocked door, found her, murdered her, and hid his victim in the closet. He apparently raped her as well. But they were still awaiting the autopsy at this point.
He goes on to request that this event be swept under the rug due to the fact that if it got out it would condemn the facility to most certain closure. He asks to let it be handled internally and apparently this is what happens, for the sake of the continuance of the facility. He asks they "pretend like the whole thing never happened."