WASHINGTON —  Four of the most popular monuments at our Nation's Capitol have been vandalized.

U.S. Park Police officials say messages written in permanent marker were discovered on the Lincoln Memorial, the Washington Monument, the World War II Memorial and the D.C. War memorial.

Graffiti is seen near the steps of the Lincoln Memorial, Tuesday, Feb. 21, 2017, in Washington. (AP/Alex Brandon)

Officials say some of the messages referenced President John F Kennedy's assassination and the Sept. 11 terrorist attacks.

"Well you almost come to expect it in this day and age. I think personally. People aren't happy with certain things and they vandalize national monuments," said tourist Vinny Lazaro.

With the Lincoln Memorial in the background, people look at graffiti on the Washington Monument, Tuesday, Feb. 21, 2017, in Washington. (AP/Alex Brandon)

The National Mall and Memorial Parks monument preservation crew says it's removing the graffiti using a mild, gel-type architectural paint stripper that is safe for historic stone.