A father charged with killing and nearly decapitating his two-year-old son with a knife demonstrated on a doll how he slashed the boy's throat in an interview with detectives, prosecutors say.

It is alleged that Rolando Ortiz tried to kill himself after he stabbed toddler Mateo Garcia Aguayo to death on Wednesday (21 February) in their Chicago, Illinois, apartment.

The 37-year-old has allegedly admitted to his child's murder whilst he was in custody. He was denied bail by Judge Mary Marubio who said Mateo's death showed "heinous behaviour indicative of wanton cruelty."

After the alleged murder, which took place at around 2pm, Ortiz allegedly called his sister-in-law and told them, his son "was with God and that he killed his son," according to authorities.

The Chicago Sun-Times is reporting that the child's spinal cord was severed and was only connected by skin and tissue.

It was reported that the alarm was raised by family members who lived below their apartment, who were notified by Ortz's sister-in-law. When police arrived the child was found unresponsive and pronounced dead at the scene.

The family member allegedly found the boy in a bin bag inside the flat. A medical examiner said the child died from a wound to the neck.

According to WGN9 News Ortiz, who was working a night shift, was frustrated because he could not sleep during the daytime because the child was running around.

Ortiz then allegedly put the boy on the floor and stabbed him repeatedly until he realised what he had done and attempted to commit suicide, police said.

Assistant State's Attorney Jamie Santini, said: "The defendant pinned the child on the floor so that the child could not move.

"As he held the child down, the defendant reached over and grabbed a large kitchen knife from a nearby table. The defendant then held his son down with one hand and used the knife in the other hand to saw across the child's throat multiple times, killing the 2-year-old."

Ortiz then allegedly jumped in his car and fled before he was apprehended by police about four hours later.