The sexual assault charges against fired Damien Memorial School band director Peter Rucci stem from a three-month relationship the 62-year-old Rucci had with a 15-year-old girl, Deputy Prosecutor Ayla Weiss told a state judge Wednesday.

Weiss made those comments after an Oahu grand jury returned an indictment charging Rucci with four counts of first-degree sexual assault and five counts of third-degree sexual assault. The mandatory penalty for first-degree sexual assault is a 20-year prison term.

Acting Circuit Judge William Domingo confirmed Rucci’s bail at $150,000. Rucci posted the bail Saturday, after Honolulu police charged him.

According to the indictment, Rucci committed eight of the charges on June 4 this year. The ninth charge alleges that Rucci had sexual contact with the girl between March 1 and June 4.

Police said the charges involve a teenage girl in Kailua. A Damien spokesman said the alleged sexual assaults happened before Rucci was hired as the school’s band director and do not involve a Damien student.

Damien hired Rucci as its band director in August. The school fired him last week after his arrest.

Rucci was also the band director at Le Jardin Academy in Kailua this year, working on the middle school and high school campuses, according to a school newsletter. Rucci said he is a Navy retiree and had also worked at Waldorf School as its orchestra director but left that position for Damien for better employment opportunities and more hours.