Neighbors were in shock Tuesday morning after police said an infant, her 4-year-old sister, and their father were shot dead Monday night in a domestic incident that left the mother — the suspected shooter — hospitalized in critical condition.

Officers responding to a report of gunshots found the man, 35, inside a rowhouse, fatally shot in the head when they arrived at the house about 9:50 p.m. in the 6300 block of Hegerman Street in the city’s Tacony section.

The older girl and her 10-month-old infant sister were rushed to St. Christopher Hospital for Children. Police halted traffic on nearby streets so the children, who were both shot in the head, could be driven as quickly as possible to the hospital. Both girls were later pronounced dead.

The injured woman, 28, was found lying on a gun, police said. She was listed in critical condition at Jefferson Torresdale Hospital.

Acting Police Commissioner Christine Coulter, who joined her officers at the scene, said the woman had apparently shot the others before turning her weapon on herself.

The commissioner said the woman and the slain man were thought to be the parents of the injured children. She said there were no other suspects in the shootings

On the quiet, residential block Tuesday morning, Anachelys Martinez, 23, who lives next door to the family’s home, said she heard gunshots Monday night, then called 911.

“It’s even horrible thinking about it,” she said. “I met them and I said, ‘Hi,’ but I never got to know them personally.”

She said the family moved in about the summer of 2018. “The only thing I can say is they were fighting all the time,” Martinez said. “I even expected something like this to happen.”

She and other neighbors said the couple had mostly kept to themselves. They did not know the names of the four family members, and police did not yet release any names.

Mary Munizza was sitting on her front steps Tuesday morning with her two grandsons, who live across the street.

“We were all bawling our eyes out and didn’t get any sleep,” she said, explaining why her grandsons Josh, 16, and Kyle, 7, were not in school Tuesday.

Munizza, 62, said she had heard from another neighbor that the mother and father of the two girls were separating. The father didn’t appear to be living at the home for the past couple of months, she said.

Although police said they had paperwork indicating the older girl was 4 years old, Josh and Kyle Munizza said she was 6 and was in first grade. The two boys said the older girl often played with other kids on the block.

“The little girl was just like her dad — the infectious smile,” Mary Munizza said. She was often seen outside skipping and was friendly, she added.

During the morning, loved ones of the father who was killed arrived to the house, but did not want to talk to reporters.

One woman who arrived by car said the man was her brother. She then joined others outside the house in a group hug. As they cried, another woman in the group collapsed onto the sidewalk in grief.