A mom was shot and killed and her two kids were hurt when bullets rang out inside a Bronx building early Saturday — and cops were hunting for the gunman, who may be the victim’s boyfriend, authorities and sources said.

The 40-year-old was shot in the torso, her 8-year-old son was shot in the left arm and her 16-year-old son was struck in the buttocks in an apartment at 226 East 203rd St. near the Grand Concourse around 5 a.m., an NYPD spokesman said.

Rescue workers tried to save the mom, but she was pronounced dead at 6:12 a.m., cops said.

The 8-year-old was taken to Jacobi Hospital and the teen was being treated at St. Barnabas Hospital, cops said.

They were expected to survive.

A trail of blood could be seen from the building’s entrance, leading into the lobby, up the stairs, and to the fifth floor where the shooting occurred.

One neighbor heard a man and a woman yelling at each other before the killing.

There was “a lot of yelling, between a man and a woman going ah ah ah. I didn’t hear the shot. It’s sad,” said Haruka Arjona, 34, who lives on the fourth floor.

The family has lived in the building for about two years, said another neighbor who declined to give her name.

“She was very friendly. We always said hi, bye,” the neighbor said.

Police were searching for a male suspect between 30 and 35 who was last seen wearing a black hat, black jacket, and brown boots, cops said.

No further information was available about his relationship with the victims, police said.

Additional reporting by Dean Balsamini and Joe Marino