(Kelly Cat notes) This event took place during the last years of Mencken's life, after he was disabled by a stroke and a major heart attack.
One lazy afternoon, while Mencken was sitting in the garden, half asleep, a squirrel came over the wall, climbed up his leg, and perched on his shoulder. "He grew fond of the animal and could summon him by whistling and he had August (Mencken Jr., his younger brother) go out and buy a large bag of peanuts with the shells on," the journalist H. Allen Smith recounted. The squirrel became a steady visitor, coming from the park across the street to sit on Mencken's shoulder. A week or two went by with no sign of him and then Henry insisted that they cross the park and search for him. "He may be sick," said the man who was the scourge of the '20s. They went over and found the tree where the squirrel lived, and they scattered peanuts around. Now the squirrel started crossing the street to visit his friend again.
There came an afternoon when Henry and August were sitting out front; they saw the squirrel come out of park and start loping across Hollins Street. Suddenly an automobile swished by, killed the squirrel, and went on without slackening speed. Henry was livid with rage. He cried out against the driver of the car, insisting that the man hit the squirrel deliberately, calling him a murderer and worse, howling that the gallows would be too good for such a villain. "He got madder at that man," said August Mencken, "than he ever got at the Anti-Saloon League."
Found in Mencken: The American Iconoclast by Marion Elizabeth Rodgers (2005: Oxford University Press). Thanks tons, Kelly Cat. You're the best. Everybody go say so at It's All Good!