Irving police rushed to the Windtree Apartments on Esther Road after the mother called 911 at about 5 p.m.
A 5-year-old Irving boy and his 2-year-old sister have both died after their mother allegedly strangled them with a wire, police said.
Police rushed to the Windtree Apartments on Esther Road after the woman, 30-year-old Saiqa Akhter, called 911 at about 5 p.m., indicating she had done "something terrible" to her children, police said.
"I don't have exact verbiage, but it was something along the lines of, 'She has done something terrible to the children,'” said David Tull, Irving police spokesman. "The mother was the only caretaker in the house at the time of this incident, and the father was not here."
When officers arrived, they found Zain Akhter, 5, and Faryaal Akhter, 2, in serious distress.
"They looked passed out,” said neighbor Gilbert Medina. “They got carried out and taken to the ambulance."
Zain was pronounced dead at the hospital. Faryaal was listed in “very critical” condition Monday night. On Tuesday, her prognosis grew more grim, with doctors saying she was not expected to survive. At 6:30 p.m., she was pronounced dead.
Detectives were questioning the mother at police headquarters. Akhter's Tuesday court hearing was delayed until Wednesday morning. Police said they plan to charge her with capital murder.
There was no immediate word on the mother's motivation.
Wasimul Haque said that Akhter, his niece, had been depressed since moving to a new apartment.
"It looks like she had mental problems," Haque, of Irving, told the Dallas Morning News. "I don't understand why she did it."
Anna Brandon, a psychologist at Southwestern Women's Mental Health Center, said it's possible that Akhter had deeper troubles.
"Close to 75 percent of women who kill their children have a psychiatric illness," she said.
Brandon said common risk factors in women who kill their children include a lack of social support and resources to deal with stress.
"Families today face an increasingly complex environment in which to raise their children," she said. "Stress levels are high and to admit that one is having difficulty is not weak, it's strong."
Neighbors said the children seemed happy.
"(They were) just little friendly, happy kids, the kind that like to come outside and play,” said longtime resident Ann Kohanow.
NBCDFW's Ken Kalthoff contributed to this report.