Marisol Bello

USA TODAY

MECHANICSVILLE, Va. — Kristi Hooper called her husband's cellphone on a mild January morning eager to hear her 3-year-old twins squeal with laughter as they gave her a rundown of their morning with their dad.

It was the Saturday morning routine that she and the girls, Caroline and Madison, and her estranged husband established after the couple separated four months earlier.

This time, he didn't answer.

She called what seemed like a hundred times in between waiting tables at a restaurant.

No answer.

After work, she drove to her husband's home. The blinds were drawn. His cars were in the driveway.

As she got to the front door, she could hear an incessant high-pitched beep that sounded like an alarm. She ran to the side door and saw her husband's van running with a hose attached to the exhaust pipe.

In that moment, even before she followed the hose through the mudroom, up the stairs and into her daughters' bedroom, she knew what he'd done.

"I always thought he might kidnap the girls," she says. "I never thought he'd hurt them."

When a parent deliberately kills a child, the crime — called filicide — captures the attention of a public horrified and fascinated by the violation of a central edict of parenthood: to keep a child from harm.

The issue is back in the news with several recent incidents.

South Carolina dad Timothy Ray Jones has been charged with murdering his five children in September. Police say he confessed to killing them and burying them on a country road in Alabama.

A Georgia father, Justin Ross Harris, waived his arraignment this week, pleading not guilty to murder charges that he intentionally left his 22-month-old son, Cooper, strapped in his car seat for nearly seven hours in a hot SUV in June.

Annually about 450 children are intentionally murdered by a parent.

More than three decades of FBI homicide data shows patterns stand out when parents kill their children: Three out of four child victims are younger than 5. In 56% of all cases, fathers are the killers. In murders with multiple victims, fathers are the culprit 70% of the time.

Northeastern University criminologists collected the data and applied statistical models to the records.

Many of the incidents involve parents who are divorcing and often in custody battles, says Kathleen Russell, executive director of the Center for Judicial Excellence. The organization has tracked at least 287 cases since 2008 of parents involved in custody fights who killed their children.

There are scattered efforts to train court personnel on how to spot potentially dangerous parents in custody cases. The U.S. Department of Justice is currently working with courts in Cook County in Chicago, the state of Delaware, Hennepin County in Minneapolis and Multnomah County in Oregon (which includes Portland) to identify the procedures and practices that put children in harms way.

While men are more likely to kill several relatives at once, they are also more likely than women to kill themselves afterward, says Jack Levin, a Northeastern University criminologist who studies mass killings.

"They may feel like they've suffered a catastrophic loss … and they go on a suicidal rampage," Levin says.

Hooper had no idea that her family would fit such a horrific pattern.

A Happy Start

When Kristi Hooper, a single mom raising her son from a previous marriage, met Robert King in the fall of 2007, she thought he was the answer to her prayers.

She was waiting on his table at the restaurant where she'd worked for 20 years and he was cracking jokes with his friends. When he asked for her number, she was happy to give it to him.

"He was funny and energetic," she says. "My son and I had been alone for eight years, and he treated me like a queen."

She longed for the companionship and laughter King seemed to provide. It was a whirlwind romance, capped when King asked her 8-year-old son if he could marry his mother. King and Hooper married in April 2008.

By then, they knew Hooper was pregnant with twins.

Caroline and Madison struggled just to be born. The identical twins suffered from twin-to-twin transfusion syndrome, a life-threatening condition in the womb in which one twin has to pump blood to the other. The girls were born on Aug. 15, 2008, by Caesarean section more than two months prematurely. They each weighed a little over 2 pounds.

They stayed in the hospital for more than two months with oxygen tubes and IVs attached to their bodies. Slowly, they gained weight and grew healthy.

At home, all seemed fine at first. Hooper says King was supportive. He washed bottles and fed the girls.

The girls grew into bubbly, smart bundles of energy with no signs of the condition that had threatened their lives. They loved cupcakes and Thomas the Tank Engine.

But King changed. At first, Hooper says, he yelled at her for small things. If she didn't check the lint in the dryer or if she left her phone charger plugged in without the phone, "he'd go ballistic," she says.

In time, she says, he began to belittle her constantly.

"He told me I was mindless and irresponsible," she says. "He pushed me to the lowest levels of my self-esteem."

Her breaking point came when she says he told her he had shoplifted thousands of dollars worth of clothes and diapers for the girls while they were with him.

"He was angry at me for being angry," she remembers. "He risked our whole family, but he thought I was at fault.

"I knew I had to get out. He had no real sense of reality or reason."

She moved out with her three children in September 2011.

The following month, King filed for divorce and sought custody of the girls, accusing Hooper of abandonment.

She says he harassed her daily with text messages and phone calls. One minute, he told her she was a horrible person and threatened to take the children; the next, he apologized and invited her to dinner.

"That sounds like he was a classic terrorist," says Janice Rosa, a retired New York State Supreme Court judge who specialized in family law as a practicing attorney and judge. Today, she trains judges to spot potentially dangerous parents in custody cases. "He used reward and punishment to get her to do what he wanted."

That behavior should have been a red flag to the lawyers and court personnel assigned to the divorce case, Rosa says.

Hooper says they had a temporary agreement in which she had the girls during the week and he had them on the weekends. She says once when she went to pick up the girls at his house, he wouldn't let her see them and let the girls leave only after his lawyer called him.

Hooper says she pleaded with her attorney, Mary Wilkins Hunt, to push for an emergency hearing so a judge could hear about his erratic and controlling behavior. She says she was afraid he'd run off with the girls. But Hunt, she says, told her their case didn't meet the criteria for an emergency hearing.

Through a secretary in her Richmond, Va. office, Hunt refused to comment.

The court appointed a guardian ad litem, an independent advocate for children. Hooper says they met once. The guardian, attorney Adrienne Barnes, did not return calls for comment.

Hooper says the court ordered a psychiatric evaluation of both parents, but a date was never set.

On the afternoon of Jan. 28, 2012, Hooper ran inside her estranged husband's house.

The door to the girls' bedroom was open, but a blanket hung from the doorway. She yanked it down and saw her little girls lying on the bed. They were covered in blood.

Hooper tried to pick up the nearest girl, Madison, but her body was cold and hard. It is a scene that replays in her mind constantly.

King left a one-sentence note: "I will not subject my daughters to their mother's psychological issues."

Besides rigging the carbon monoxide from the van, King had slit the girls' throats and his own. The combination killed all three, the medical examiner said.

A Home Becomes a Shrine

Today, Hooper, 44, lives with her 16-year-old son and her mother, Julia Linden, 64, a retired nurse. Their home is a shrine to the two little blondes with cherubic faces and brown eyes.

Two colorful ride-on toy cars are parked side by side in the kitchen. Photos and paintings of the twins crowd every wall.

Near the door, two matching pink-hooded sweaters hang on pegs where the girls left them.

Hooper and her mother are reminded at every turn of the horror that devastated their family. The blinds are drawn. They rarely leave the house.

Hooper hasn't been able to hold a steady job. She's had six jobs in the past year and lasted two days in the most recent one, in June. She no longer has insurance to cover counseling. She and her mother have been diagnosed with post-traumatic stress disorder.

"Some days I don't know how we go on," Linden says.

What keeps them going is Hooper's son. "I wouldn't be here if not for him. He's been through something no teenager should have to go through," Hooper says.

She hopes her experience, particularly in the court system, can be a lesson for other families and authorities.

"Trust your gut and fight," she says. "Make people you are paying listen to you. They wouldn't listen to me."

Thumbing through a stack of photos of the girls, Hooper can't escape the joy in her daughters' faces as they laugh with dimpled cheeks into the camera.

Looking at the girls in matching dresses in their one and only pre-school photo, she can't help thinking of what their lives might have been.

And she can't escape her grief as she strokes their faces in one final image. They are dressed in matching pajamas so "they would be comfortable," she says. Their eyes are closed as they lie side by side in their casket.

Contributing: Meghan Hoyer