MINNEAPOLIS — A Minnesota man has apologized for vandalizing a beloved national monument in Montana, saying he carved his and his new wife’s name into the soft rock of Pompeys Pillar because he was afraid she might have breast cancer.

Cole Randall, 23, of Plymouth, apologized in an email sent to the federal Bureau of Land Management and to media outlets.

“I regret my decision and … I humbly apologize to the people of Montana and to every American who was affected by my foolishness,” Randall said in his email. “I hope you can find it in your heart to forgive me for this and realize that I understand the gravity of my mistake.”

Pompeys Pillar lies 30 miles east of Billings, and is notable for the signature of Capt. William Clark — half of the Lewis and Clark Expedition — in 1806. Randall’s carving was made just a few feet to the left of Clark’s.

Randall and his wife were interviewed by authorities after an alarm was triggered at the monument on Oct. 10. It was closed at the time due to the federal government shutdown. The new carving on the monument was discovered a week later.

Federal investigators were assessing damage before deciding whether to bring criminal charges.

In his email, Randall said he and his wife had been honeymooning in California when she discovered a lump on her breast. He said they cut their honeymoon short and he was worried his bride might have cancer.

He said he was inspired during their stop at Pompeys Pillar by a description that said generations of Americans passing by had left their marks on the rocks, and decided to leave the couple’s name in case anything happened to her.