A three-year-old boy and an 11-month-old boy were found stabbed to death in a Bronx family shelter apartment on Saturday evening, according to police.

New York City Police Department (NYPD) Deputy Chief Louis De Ceglie told reporters that the children were found with multiple stab wounds to their necks and torsos at 246 Echo Street in the Mount Hope neighborhood. The mother of the children has been placed in custody and is a person of interest.

Before the tragic finding, police responded to a report at the same location at around 7:20 p.m. of a woman who was behaving erratically and lighting things on fire in her kitchen. She was noted to be non-violent and had no weapons on her.

When officers arrived, they found a 24-year-old woman naked inside the apartment on the third floor, where she was “acting irrationally.” She was taken into custody without incident and transported to St. Barnabas hospital without incident at 7:50 p.m.

Before the woman was brought to the hospital, a family friend told police that the woman’s children were with her father.

Five minutes after the woman was brought to the hospital, police received a second 911 call reporting that two small children were unresponsive at the same location on 246 Echo Street.

Police returned to the family shelter and found one of the boys on the floor and the other on the bed with multiple stab wounds.

NYPD officers and another family member attempted to resuscitate the three-year-old and the 11-month-old before being transported to Columbia Presbyterian Hospital, where they were pronounced dead.

The two children were believed to have been in the bathtub the first time police arrived at the apartment, according to a police source via the New York Post.

The mother was later taken into custody as a person of interest but has not been arrested, said De Ceglie. He added that an incident had occurred at the location in the past, but it happened a couple of years ago.

One neighbor, Charlotte Obiri, 47, told the Post that she heard the couple fighting earlier in the day.

She later heard the father screaming “hysterically” and saw him carrying the boys, who were covered in blood.

“They were dead. They were dead. There was blood everywhere, it covered them,” Obiri said. “It’s horrible. It’s heartbreaking.”

De Cecile commended the police officers who responded but noted that the horrific incident would stick with them for a long time.

“The police officers who responded, I think they did a great job,” De Ceglie said at the press conference. “It’s something that they are going to have to live with and think about, probably for the rest of their lives.”

Before Saturday’s incident, there had been 12 homicides reported in the NYPD’s 46th precinct–where the family shelter is located–since this time last year, according to NYPD crime statistics.

You can follow Ethan Letkeman on Twitter at @EthanLetkeman.