ALTON, N.H. — Authorities in New Hampshire have filed an additional charge of second-degree murder against an 11-year-old accused of shooting dead a man and his wife.

Officials say James Eckert, 48, and his wife, Lizette Eckert, 50, were found Friday morning inside a home in Alton with gunshot wounds. He was pronounced dead late Friday after he was taken to a hospital in critical condition. She was pronounced dead at the scene. Autopsies revealed they died from a single gunshot wound to the head.

Authorities arrested and charged an 11-year-boy with one count of second-degree murder and one count of attempted murder in connection with the case. He was charged Tuesday with the second count of second-degree murder.

Authorities have not said if the boy has any connection to the Eckerts. The investigation is ongoing.

The couple, both chiropractors, had ties to Maine. They previously lived in Raymond and operated Innate Chiropractic in South Portland for more than a decade in the late 1990s and early 2000s, according to former employees who remained friends with the Eckerts.

Jenifer Edwards of Portland worked for the Eckerts in 2000 and told the Portland Press Herald she was struck with horror when she learned that the couple had been killed.

“They were tremendous people,” Edwards said. “They were very community oriented. They believed that the body had an innate ability to heal itself.”