COTTAGE GROVE, Wis. -- The Dane County Sheriff's Department is investigating an early-morning home invasion in which an intruder pistol-whipped two residents.

Around 1:39 a.m. Saturday, Dane County sheriff's deputies and Cottage Grove police arrived at a residence on County Highway AB in the Town of Cottage Grove on a report of a home invasion.

Officers said that a lone gunman entered the apartment and assaulted two residents.

Responding officers said they found a 63-year-old man and a 55-year-old woman who had been pistol-whipped by the assailant. Both were taken to a local hospital with head injuries that were called serious but not thought to be life-threatening.

Authorities said the assailant was described as a white male, 5 feet 6 inches to 6 feet tall, clean shaven with a stocky build. The man was dressed all in black clothing and might have had on a hooded sweatshirt.

The Dane County Sheriff's Office said it is investigating the incident at the request of the Cottage Grove Police Department. Dane County Sheriff's Office detectives and crime scene personnel were called in to assist with the investigation.

Authorities said that anyone with information about this incident or any other crime is encouraged to call the Dane County Sheriff's Office Tipster Hot Line at 608-284-6900. Callers can remain anonymous and might be eligible for a cash reward.