A Bronx teen who allegedly stabbed his three younger siblings is under arrest and was taken for a psychiatric evaluation, police say.

The 17-year-old allegedly stabbed his two brothers, ages 6 and 13, and his 9-year-old sister. The younger brother is in serious condition, while the other two siblings are listed in stable condition, authorities say.

Neighbor Delila Flores says one of the boys ran down the stairs inside a Clay Avenue apartment building chased by his older brother. Flores says her son grabbed the 17-year-old from behind and took the knife away.

Police charged the teen with assault.