A Kona man faces up to 140 years in prison after he was convicted of sexually assaulting two young girls over a period of seven years, according to the Hawaii County Prosecuting Attorney's office.

Derek Mark Cavillis, 39, of Kealakekua was convicted Friday of 10 felony counts of sex assault against 5 and 8-year-old girls.

The offenses happened between 1999 and 2006, but the girls kept silent after being threatened by Cavillis.  Both girls are acquaintances who were under his custody during the offenses.

Prosecutors were able to convict Cavillis based on testimony from the two girls and a confession Cavillis made to police prior to his arrest.

He was scheduled to be sentenced in Kailua-Kona on September 10.