Arrested in slay of his brother

A man stabbed his brother to death inside a NYCHA apartment across the street from NYPD Headquarters in lower Manhattan — then confessed to nearby cops while still holding the bloody knife in his hand, police sources said Sunday.

“I just murdered my brother,” the 50-year-old sibling, Triquang Lau, told an NYPD lieutenant outside Police Plaza about 3:25 p.m. on Saturday, sources said.

The confession came moments after he allegedly stabbed his brother in an apartment in the Smith Houses on St. James Place near Catherine Slip.

The alleged stabber spoke only Chinese and walked up to an Asian lieutenant he saw outside the building to make his confession, sources said.

A neighbor who lives on the same floor as the brothers was startled when he opened his door to a hall full of police officers, some of them performing CPR on the victim.

“I thought he had a heart attack. There were plenty of cops out here, and I’m wondering why there are so many cops if someone had a heart attack,” said Daniel Paniagua, 61. “They were doing chest compressions on him.”

“I didn’t hear anything. If it happened, it was quiet,” he said, adding that three brothers lived in the apartment. “I don’t hear any noise. The apartment is always quiet.”

First responders found the mortally wounded sibling in the apartment and rushed him to New York-Presbyterian Hospital Lower Manhattan, but he couldn’t be saved. His name was not immediately released.

Lau was charged with murder. He was awaiting arraignment in Manhattan Criminal Court on Sunday.