MADISON, WIS. ? An inmate at Wisconsin’s toughest prison could face more time for allegedly hiding urine in a tube of toothpaste and squirting it at a guard.

Jonathan M. Krueger, a 23-year-old inmate at the Wisconsin Secure Program Facility, faces charges of assault by a prisoner in the May 29 incident.

According to a criminal complaint, Krueger admitted to spraying a guard with urine he had put in a toothpaste tube when the guard came to his cell to pick up his food tray.

Krueger told investigators in June he thought it would be funny to squirt the guard, the complaint said. He told them he now thinks it was “very disgusting and wrong.”

If convicted, Krueger could get an additional 3 1/2 years behind bars and face up to $10,000 in fines.

The Department of Corrections did not immediately return a message left by The Associated Press on Saturday seeking information on why Krueger is being held at the facility.