(Reuters) - A terminally ill former Wisconsin deputy sheriff was charged on Friday with murder in connection with the fatal shootings of his wife and her sister in his home last week, court documents showed.

Andrew Steele, 39, was charged in Dane County Circuit Court with two counts of first-degree intentional homicide in the Aug. 22 deaths of his wife, Ashlee Steele, and her sister, Kacee Tollefsbol, in Fitchburg, Wisconsin. Steele, arrested after the shooting, is in jail on $1 million cash bond.

A criminal complaint filed by police does not give a reason for the killings. It says Steele had been diagnosed with a terminal illness and his wife had helped organize fund-raisers to help pay for his care. The Wisconsin State Journal identified his illness as amyotrophic lateral sclerosis, also known as Lou Gehrig’s disease.

Steele's lawyer, Jessa Nicholson, said she was exploring whether there were medical or psychological factors in the shootings. Steele has not yet entered a plea.

"There is no apparent history of domestic violence and no apparent motive for these actions and the allegations," Nicholson said, adding that Steele left his job as deputy sheriff in June for medical reasons.

According to the complaint, Tollefsbol called 911 to report that Steele had shot her in the back in the basement of his home. Officers found her on the floor saying “I am dying, I am dying,” and she was later pronounced dead at a hospital, the complaint said.

Officers found Ashlee Steele dead in bed under a comforter, shot in the head, with a plastic zip tie device around her neck, according to the complaint.

Andrew Steele was at the house lying on the laundry room floor next to a 9mm handgun but not injured, the complaint said. He had lit a charcoal-burning stove in the room and carbon monoxide detector alarms were sounding, the complaint said.

(Reporting by Kevin Murphy in Kansas City; Editing by Cynthia Johnston and Mohammad Zargham)