A 90-year-old man who was once a principal at a private school on Maryland’s Eastern Shore has been arrested and charged with sexually abusing two teenage girls at the school in the 1960s.

Maryland State Police said Russell Isaac of Bowie, Md., faces multiple charges of rape and other sex offenses. He was arrested Monday at his home and is being held at the Prince George’s County jail, according to officials.

The investigation into Isaac began in May 2016 when a woman came forward and said that when she was a 14-year-old student at W.C. Moffett School in Barclay, Md., in the late 1960s, she was abused by Isaac. During the investigation, police said, another woman also alleged that Isaac had sexually abused her at the school when she was 15.

Police said the incidents took place between 1966 and 1968.

It was not clear immediately from online court records whether Isaac had a lawyer.

Russell Isaac, 90, of Bowie, Md., is accused of sexually assaulting two teenagers at a private school on Maryland's Eastern Shore in the late 1960s. (Courtesy of Maryland State Police)

Authorities said that the case remains under investigation and that they believe there may be additional victims.