UTICA — What kind of jerks scrawl graffiti at a public park and desecrate an ancient Native American gathering place?

Thankfully, they're the kind dumb enough to somehow let their horrible handiwork be captured on social media.

Monday, two visitors at Starved Rock State Park — a man and a woman, both apparently in their 20s — scribbled dark-hued messages on what is known as Council Overhang, a cavern-like formation on the east end of the park, said Park Superintendent Kerry Novak. Later, a photo of the pair and the vandalism was posted on Instagram, prompting an ongoing investigation by Illinois Conservation Police.

"It's disrespectful," Novak said. "If you bring your family here, you want to see a beautiful natural area. You don't want to see this sort of thing."

Monday, a witness came to the Starve Rock administration office and reported seeing two people deface a wall of Council Overhang, a sandstone formation used for 8,000 years as a Native American gathering place. The witness also overheard one of the two say something about posting a photo on Instagram, Novak said. Later, on Instagram, a staffer found the photo of the two — including the male apparently giving the peace sign — in front of the graffiti.

"They seemed pretty proud of it," Novak said.

Novak isn't sure what was used to scrawl on the wall. The photo shows "B+K" inside a heart, but the other wording appears unclear.

It's unclear who took the photo of the pair. Further, citing the police probe, Novak did not want to say on whose Instagram account the photo had been posted.

After the shot was shared on Facebook page for State Rock and Matthiessen State Parks, tips began to pour in. Further, some of the tips indicated a separate, earlier instance of vandalism, at someone else's hand, Novak said. That act, involving carving into another park wall, also is under police investigation.

Any further tips called be called in to the park at (815) 667-4726.

Novak says vandalism at the park has been on the increase over the past few years. He said he did not have a cost estimate to clean the defiled wall.

"It's very difficult to get this stuff cleaned up," Novak said.

PHIL LUCIANO is a Journal Star columnist. He can be reached at pluciano@pjstar.com, facebook.com/philluciano and (309) 686-3155. Follow him on Twitter.com/LucianoPhil.