DOYLESTOWN, Pa.—The off-duty New Jersey police officer arrested at his estranged wife's Philadelphia-area home faces 13 counts of attempted homicide following a 10-hour standoff in which he opened fire with a high-powered rifle.

Investigators are still trying to determine exactly what sparked the standoff in Doylestown, Bucks County involving a Clifton Township, N.J., police officer.

Forty-two-year-old Richard Klementovich was taken into custody late Sunday night. The standoff started just before 2 p.m. after police were called to the home over a neighborhood dispute.

Authorities say officers were under fire as soon as they arrived at the home. One officer suffered minor injuries from shrapnel.

Officials say Klementovich eventually surrendered to negotiators. He was arraigned early Monday on dozens of charges including aggravated assault. Court records don't list an attorney for him.