A relative of the Brooklyn man shot by NYPD cops after he stabbed his young daughter and three nieces with a meat cleaver had feared he would lose control one day — and kill everybody in the house, a police source said Monday. Months before Longqian Chen, 49, allegedly attacked the four girls Sund ay with a meat cleaver and large knife in their Bensonhurst home the relative filed a complaint with the city’s Administration for Children’s Services describing him as potentially dangerous to family members, police sources said. Chen was diagnosed last year as bipolar and schizophrenic, according to police sources. He was shot once in the head and twice in the chest in the morning confrontation with police. He later underwent surgery at Maimonides Medical Center and is now in stable condition, police said. If he recovers he will likely be charged in the brutal assault in which he allegedly attacked his 16-year-old daughter and three nieces, ages 8, 11 and 13. Chen has no arrest record but last year he was treated for bipolar disorder and schizophrenia, a police source said. It was the brave 11-year-old niece who dialed 911 as she hid in a room and told a dispatcher what was happening, NYPD Commissioner Jessica Tisch said Sunday, The girl didn’t know her exact address but police were able to trace her phone and send officers to her home on 84th St. near 17th Ave. in Bensonhurst, Tisch said. When the officers arrived they could hear screaming. Theodore Parisienne / New York Daily News; NYPDCops respond to 84th St. near 17th Ave. in Bensonhurst Sunday morning after an 11-year-old girl called police on her mentally ill uncle as he attacked her and her young sisters with a large kitchen knife and meat cleaver (insets).(Theodore Parisienne / New York Daily News; NYPD) The suspect’s 12-year-old son, who wasn’t hurt in the mayhem, led them into a vestibule with two doors, Tisch said. They heard screams coming from the door on their left so they kicked the door down and found the suspect armed with a bloody cleaver He ignored numerous commands to drop the cleaver, Tisch said, then advanced towards two officers, who opened fire with seven shots. Chen was critically wounded and police at the time though he might not survive. The children were taken to Maimonides Medical Center in critical condition. The 13-year-old girl is the most badly hurt, police said Monday. ...read more read less