A nightmare played out in Brooklyn over the weekend — fresh proof of the horrific consequences of state lawmakers’ refusal to embrace Gov. Kathy Hochul’s reforms and get the severely mentally ill the treatment they need.

In an unthinkable ordeal, four girls, ages 8 to 13, were brutally slashed with a meat cleaver by a male relative inside a Bensonhurst home Sunday morning.

Thankfully, all survived after the police arrived and shot the suspect, Long Qian Chen. But the girls will surely live with the emotional and physical scars for a very long time.

Like countless nightmare-makers before him, Chen had a history of mental illness, including reported hospitalization for schizophrenia.

Every foot-dragging lawmaker who’s squeamish about “forcing” the dangerously mentally ill into treatment should view the bone-chilling photos of the crime scene.

Chen is exactly the type of person involuntary commitment is supposed to be for — a clear danger to himself and others.