A Lower East Side man walked up to cops clutching a knife over the weekend and told them, “I just murdered my brother,” police sources said Sunday.

Suspect Triquang Au, 50, has since been charged with the murder, police said.

After Au’s alleged confession shortly before 3 p.m. Saturday, officers found 61-year-old Wilson Au, the suspect’s brother, unconscious in the siblings’ apartment on Saint James Place, authorities said.

The victim was in a seated position with a stab wound to the stomach, police said.

Wilson Au was taken to New York-Presbyterian Downtown Hospital, where he was pronounced dead, according to police.

Triquang Au was arrested and charged with second-degree murder.

Detectives from the 5th Precinct are continuing to investigate the case, police said.