Police shot and killed a man who slashed his elderly father in the head after the maniac attacked them with a large butcher knife inside the couple’s blood-soaked Manhattan apartment on Sunday afternoon, police said. Officers were called to the Ludlow Street home on the Lower East Side for an assault in progress around 4 p.m. and when they arrived they found a trail of blood leading upstairs, where they came face to face with the knife-wielding madman, the NYPD said. Paramedics respond to the scene of a police-involved shooting on Manhattan’s Lower East Side on Sunday afternoon, after Wei Chan hit his father Chung, 75, in the head with a butcher knife. Obtained by NY Post The butcher knife recovered at the scene. “NYPD officers entered the building, saw the trail of blood, and responded without hesitation, not knowing what awaited them as they walked up the stairs,” Deputy Chief Melissa Eger said at a news conference later that night. As the officers walked up the blood-stained stairs, they were greeted by a man, identified as Wei Chan, 54, who was holding a large butcher knife as he advanced toward them, Eger said. The officers repeated multiple commands for Wei to drop his large sword, which he ignored, according to the NYPD chief. “The officers responded and fired their firearms, striking the subject,” Eger said. Video from witnesses at the scene shows EMS performing CPR on Chan before he was rushed to Bellevue Hospital, where he was pronounced dead, according to the NYPD. Passersby react to the violence. NY Post Cops’ James Keivom also discovered the suspect’s father, Chung Chan, 75, with a laceration to his head on the second floor. Investigators determined that his son stabbed him. He was also rushed to Bellevue, where he is in stable condition and is expected to survive, according to authorities. A couple from Brazil who were in the city on their honeymoon were shocked by the bloody aftermath they witnessed while first responders treated the father and son. First responders carry Wei Chan, 54, to an ambulance. Obtained by NY Post NYPD officers investigate the scene at 126 Ludlow St. James Keivom for NY Post. “I thought it was a neighborhood fight,” said Fabio Gutierrez, 43, who was having dinner with his new wife, Debora Martins, at a nearby restaurant when the violence began. “We saw the guy get on the stretcher and they were giving him CPR,” Martins, 38, added. “I’ve never seen anyone who looked like they were dying,” he told The Post. “We’re tourists here; we’re not used to seeing that kind of violence. So it was really shocking to see the guy in that state.” Members of the NYPD Crime Scene Unit collect evidence at the scene at 126 Ludlow St. on the Lower East Side. James Keivom for NY Post The suspect allegedly advanced toward the officers with the butcher knife. James Keivom of the NY Post Martins said he saw police take another man covered in blood down the street. “It wasn’t good. It was all bloody,” he said. The 75-year-old man does not know his son is dead, sources said. Chan has no criminal history with the NYPD, but has a documented mental health history, police said. No officers were injured during the altercation and the knife was recovered from the scene. Mayor Zohran Mamdani said he had been informed about the officer-involved shooting and wished the wounded victim a “speedy and complete recovery.” “As with every incident in which NYPD officers fire their weapons, there will be an internal investigation and body camera footage of the incident will be released,” Mamdani said in a statement. Additional reporting by David DeTurris