In the predawn darkness, Christina Walker, 12, lifted herself off her blood-soaked bedroom floor and went to the phone. Three generations of her family — her 7-year-old sister, her mother and her grandmother — lay nearby, fatally shot in the head by her father, the authorities said.

Christina had been shot in the head, too. A bullet had exited near her eye. Her speech was muddled, her words a bit difficult to make out, according to Robert K. Boyce, the chief of detectives for the New York Police Department. But the girl pressed on, dialing 911 and even trudging downstairs to pull the door open for police officers.

In a storm of violence in Queens early Saturday, Jonathon Walker killed his younger daughter, Kayla, along with the girls’ mother, Shantai Hale, 31, and Ms. Hale’s mother, Viola Warren, 62, the authorities said. Mr. Walker, 34, then drove to a desolate area six miles away, where he fatally shot himself.

Christina, the only survivor, was taken to Long Island Jewish Medical Center, where she was in critical but stable condition in a medically induced coma, the police said.