Insets: Fernando Vega and Angelina Calderon (Harris County Jail). Background: Home in Houston, Texas, where Vega and Calderon's month-old twins died (KHOU/YouTube).

A Texas father is headed to prison for decades for shaking and beating his malnourished one-month-old twins to death after they were "crying and fussy throughout the night" before they died.

Fernando Vega, 23, pleaded guilty last week to injury to a child with serious bodily injury in the deaths of Massail and Mirena Vega. He was sentenced to 40 years behind bars. His girlfriend, 23-year-old Angelina Calderon, is facing the same charge and has a court hearing set for March 5.

A probable cause arrest affidavit said Vega discovered the twins unresponsive at their home in Houston around 11 a.m. on Oct. 4, 2023. He called Calderon.

"They are not waking up," he told Calderon. "They're not doing nothing."

Calderon then called 911.

As Law&Crime previously reported, Calderon allegedly told detectives she last interacted with the babies shortly after midnight when she went to bed. Vega said he cared for the twins during the night, calling them "fussy." He put them to bed around 6 a.m., according to officers. Calderon said they were still sleeping when she woke up around 8 a.m. and Vega dropped her off at work around 10:30 a.m. The twins' grandmother watched the babies during that time, according to the document.

Initially, police found no serious traumatic injuries on the infants.

But an autopsy told a disturbing tale. Doctors found the infants were extremely malnourished and suffered traumatic injuries on three separate occasions, according to the affidavit. Calderon told cops that despite the babies being born prematurely, she never took them to any checkup appointments with doctors, detectives wrote. The twins were also dehydrated.

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One infant had contusions on the forehead, torso, feet, and arms, along with fractures of the left femur and multiple ribs, the affidavit said. The other infant also had bruises to the forehead and arm, along with head, clavicle, and bilateral rib fractures, the autopsy determined. Those injuries were in various stages of healing, which suggested they happened during three separate incidents, authorities said.

The medical examiner determined both twins died from multiple blunt force injuries and the manner of death was homicide. Vega and Calderon intentionally inflicted the injuries and should have sought medical care, detectives wrote.

"This is a very, very tragic, heartbreaking scene," Houston police Assistant Chief Patricia Cantu told reporters. "Obviously the family is devastated."