A man accused of shooting dead his girlfriend, murdering their daughter with an ax and stabbing and setting their son alight was allowed to confront the boy in court.
During cross-examination Ronnie Oneal, who is defending himself, asked his 11-year-old: "Did I hurt you the night of this incident?"
"Yes," replied Ronnie Jr, who was eight at the time of the March 2018 attack in Tampa, Florida.
"I did? And how did I hurt you?" the defendant, 32, followed up.
"You stabbed me," his son replied.
The exchange came after Oneal was granted permission to lead his own defense by a judge who deemed him sufficiently mentally fit and educated.
Since starting his own defense on Monday, Oneal has sought to portray himself as the victim of a conspiracy.
"By the time it's all said and done, you will see who is the mass murderers," an animated Oneal yelled at the jury.
"This whole entire case has been tampered with and fabricated," he went on. "My son did not witness me viciously beat his mom to death."
His son, who testified via video link Wednesday from a different location, told the jury his father had killed his mother, Kenyatta Barron, and struck his sister Ron'niveya with an ax.
The extremely rare courtroom confrontation between father and son had started out with familiar greetings.
"How are you doing? Good to see you man," the accused said to his alleged victim.
"Good to see you too," replied the boy, who has since been adopted by one of the police officers who led the investigation.
The pleasantries stopped there, however, as Oneal spent 20 minutes trying to point out inconsistencies in his son's testimony, seeking to highlight gaps between his depositions and his remarks to the court.
He also made his son acknowledge that he had not actually seen his mother die. The victim had testified that he saw his father threaten his screaming mother with a shotgun.
The boy's testimony under cross-examination by his father was no less damning.
Describing the death of his sister, he said his father had "hit her with an ax in the back of the head, I saw her eyes roll."
In the United States, defendants are allowed to represent themselves and question witnesses, even if those in the stand were victims of the alleged crime being tried.
A man who opened fire on a train in New York in 1993, killing six people, questioned the people he had wounded during his trial.
This tactic often does not end well, and defendants are advised to get private representation or accept the services of public defenders.
Prosecutors said that after Oneal shot his girlfriend, he then beat her so hard with the shotgun that he broke the weapon.
If convicted, he could face the death penalty.