Mother Nature has a twisted sense of humor.

In a story that reads like a scene spawned from Henri Rousseau’s Post-Impressionist mind, a United States Navy veteran was visiting San Francisco last year during Fleet Week when he innocently decided to take a load off under a tree in the Bay Area’s Maritime National Historical Park. Sometime after he nestled in and got comfortable — he was gearing up to view the imminent Blue Angels flight show — a 16-pound pinecone (seen above) from a bunya pine fell on his head, and “crushed his skull” (internal bleeding, several surgeries and “traumatic brain injury, with severe and likely irreversible cognitive deficits”).

Sean Mace, the ailing former sailor and victim in the case, is now suing the U.S. government, the National Park Service, the Department of the Interior and the park itself (i.e. the city of San Francisco) for $5 million.

“This guy has an irreversible brain injury and he’s only in his mid-50s,” said Scott Johnson, Mace’s attorney. “He’s had two surgeries already and he is going to need a third.”

The lawsuit was filed on September 4, 2015.

More from the San Francisco Chronicle:

Bunya pines are not indigenous to the area, the lawsuit notes, and the trees in question are thought to have been planted by park staff years ago. Their seedpods, or pine cones, can grow to enormous sizes, reaching nearly 16 inches in diameter and weighing up to 40 pounds.

The suit alleges that there were no warning signs posted and no fences or netting to prevent people from hanging out under the trees, violating numerous park policies requiring the removal of exotic species that create safety hazards and mandating the installation of warning signs “necessary for visitor safety.”

Aside from its monetary implications, Mace and his lawyer hope the case will shed light on the problem and prevent such a tragedy from occurring in the park again.

Already some warnings have been posted, with signs close to the danger area reading “Danger: Giant seed pod falling from tree”.