A 14-year-old boy was slashed by an unhinged fellow congregant inside a Brooklyn schul on Monday evening, police said.

The 22-year-old attacker slashed the teen in the hand inside a synagogue on 54th Street near 17th Avenue in Borough Park around 7:20 p.m., the NYPD said.

A 22-year-old attacker slashed a 14-year-old boy at the synagogue (pictured) in Borough Park. GoogleMaps

The slasher was then taken into custody without incident.

The teen victim refused medical attention at the scene.

Sources said that the assailant is well-known in the neighborhood and frequents houses of worship.

This is a breaking story. Please check back for updates.