A central Ohio man killed his ex-wife outside an apartment when she arrived to pick up their two children, and their 13-year-old son called an emergency dispatcher to report the stabbing, police said today.

The boy called 911 after the stabbing on Sunday morning in Grove City, just southwest of Columbus. Police said the boy’s mother was picking up the three children from the father’s house after an overnight visit.

"My dad just killed my mom. He just told me to call you guys," the boy said in a recording of the call. "He just ran out and killed my mom, and she's laying in the grass in front of our apartment."

Police Capt. Jeff Pearson told FoxNews.com that, under the circumstances, the boy sounded relatively calm during the phone call. When his father took the phone, he sounded lucid and spoke as if not to incriminate himself, Pearson said.

The two had a brief argument before the alleged attack, police said. Jeremy Roberts, 38, allegedly answered his door when his ex-wife Candice Roberts, 36, arrived and retrieved a double-edged knife before the attack, police said. When police arrived, Candice Roberts was found lying in the grass with the knife still plunged in her chest, police said. Her car was still running.

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As the dispatcher called for officers to respond to the scene, the boy pleaded for police not to harm his father.

"Please, guys, don't do anything to him in front of me, please," he said. "He has no weapons."

The boy apparently then handed the phone to his father, who told the dispatcher that he didn't intend to harm anyone else and that the only weapon he had was a knife that was left outside with the body. He asked if he could kiss his children, told them he loved them, then said he was going to the front door to meet the police.

"Your sister is a good big sister ... she'll take care of you guys," Roberts told his children, reported the Dispatch.

Roberts is charged with murder and was scheduled to be arraigned today. Court records didn't list an attorney for him. Police said in 2009, they received call about Roberts having an argument with his brother and a knife was involved.

A relative who answered the woman’s phone told The Columbus Dispatch police had advised the family not to comment. The children were taken by their grandparents from the police station on Sunday.

Fox News' Edmund DeMarche and the Associated Press contributed to this report.

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