WASHINGTON — The National Park Service is investigating vandalism to several national monuments in D.C.

[related_gallery align=”right”]Cryptic messages scrawled in permanent marker cropped up at the Lincoln Memorial, the Washington Monument, part of the World War II Memorial and the D.C. War Memorial over the Presidents Day weekend, park service officials said Tuesday.

The graffiti at the Washington Monument was removed by Tuesday evening, the park service said via Twitter; work at the other sites will continue on Wednesday.

One of the messages found at the Lincoln Memorial read “Jackie shot JFK” and referenced the Sept. 11, terror attacks, said U.S. Park Police spokeswoman Sgt. Anna Rose. Some of the messages are illegible, she said.

“Today, it’s certainly an ugly scar,” said NPS spokesman Mike Litterst. “A month from now, the millions that come here to see it won’t even be aware that this happened.”

Earlier, Litterst told NBC Washington the messages were likely written by just one person, based on the similarity of what was written and the handwriting style.

WTOP’s Kate Ryan and Jack Moore contributed to this report.

Editor’s Note: This story was updated on Thursday, Feb. 23 to include a fourth monument that was also vandalized, the D.C. War Memorial.