The interview occurred in the hours after A.J. allegedly killed his parents, Antonio and Dawn, at their southwest Houston home in July 2016.
Houston Police Department officer Jimmy Dodson took the stand Thursday. Dodson interviewed A.J. on the morning of his parents' deaths, testifying that A.J. was calm and emotionless.
He told the jury A.J. never cried, never got upset and never admitted any fault.
A.J. described the day before his mother and father were killed, and said nothing was out of the ordinary. He said he was still up at 1 a.m., and as he walked down from the third floor, he heard two gunshots and saw an intruder run.
"I just, like, personally felt bad because, I like, saw the guy. I feel like I should have done something," A.J. said during the interview.
Detectives: "What did he look like?"
A.J.: "They had... It was like a mask and you could only see the eyes and the mouth, but it looked like a black guy."
Later in the interview, A.J. says he never touched his dad's gun, but then, changes his story when police say they found a bullet hole in his bedroom floor.
A.J. then admits he shot the gun two or three weeks before the incident.
About halfway through the interview, A.J. says, "There will be no gunpowder, nothing like that will come back on me. I had nothing to do with this."
Dodson was asked why he didn't consider any of the other family members on scene that morning to be possible suspects, specifically A.J.'s older brother, Josh Armstrong.
Earlier in the week, the defense appeared to suggest that the killer is actually Josh.
Dodson said that after speaking with them, he had no reason to believe anyone else committed the crime.
"No one else got into the house," the detective said during the interview.
Jurors also heard A.J.'s taped interview with the magistrate judge, who read him his rights after the murder. A.J. was heard saying, "Do you know how my dad is?"
On Wednesday, jurors heard the 911 call A.J. made after the murders. He told dispatchers, "It's all my fault."
But the defense argues it's not a confession. A.J.'s attorneys claim the teen later told police he meant he was sorry he couldn't stop the intruder in the house.
A.J. broke down in tears when prosecutors showed pictures of his mother shot in bed.
"The CSU expert was a textbook example of incompetence. He did not know where the alarm system was in the house, he didn't know where the sensors were. I think he testified that there might have been 5,200 sensors in there. All that stuff is not true. He had no idea regarding the vast majority of the layout of the house after being there for seven hours. That's reasonable doubt," said defense attorney Rick DeToto.
On Thursday, the defense asked the judge for a mistrial after the prosecutors' witness mentioned a piece of evidence that the judge ruled would not be admissible in court.
The prosecutors' witness mentioned what they thought was a crack pipe found in A.J.'s room. It was later determined that it was not a crack pipe, which is why the judge denied it being discussed in the trial.
The judge left the courtroom to consider, but ultimately ruled no.
Big takeaways from today at #ajarmstrong trial: we heard AJ's 911 call; we saw AJ break down in court when prosecutors showed pictures of his mother, Dawn, shot in bed; we saw hard evidence like the gun, shell casings, bloody pillows. #abc13 Catch up here: https://t.co/6mEJCHXH3t— Courtney Fischer (@CourtneyABC13) April 3, 2019
'It's all my fault:' A.J. Armstrong's 911 call revealed as he's on trial for his parents' murders
A.J. Armstrong murder trial: Defense shifts focus to teen's brother in killing of parents
TIMELINE: The AJ Armstrong murder case
'I'M INNOCENT': Houston teen AJ Armstrong gives his side as he awaits trial in murder of his parents
Follow Courtney Fischer on Facebook and Twitter.