On the night of 29 July, 2016, a 911 operator near Houston received a call from a concerned teenager. The young man told the operator that he heard gunshots at his home. When police arrived to check on the teenager, they found that both of his parents had been shot in the head while sleeping in their beds. The boy's mother, Dawn Armstrong, was pronounced dead at the scene. His father, former NFL linebacker Antonio Armstrong Sr, was rushed to a hospital where he died from his wounds. When police searched the house, they found the murder weapon — a .22 calibre pistol belonging to Mr Armstrong Sr — and a terrifying note. "I have been watching you for a long time. Come get me," the note read. But there was no shadowy killer waiting to play cat and mouse with the Houston police. Instead — at least so far as a Texas grand jury is concerned — the teenager who made the call, Antonio "AJ" Armstrong Jr, pulled the trigger, planted the gun, and wrote the threatening note on the night of his parents' deaths, according to the New York Post. Armstrong Jr, now 23, was found guilty on Wednesday and was sentenced to life in prison for the murder of his parents when he was 16 years old. He stood quietly in the courtroom when his verdict and sentencing were read out. His wife — who was dating him at the time of the murders — sobbed. Jurors spent approximately 10-and-a-half hours deliberating before ultimately deciding Armstrong Jr was guilty. It was his third time at trial; the first two ended with hung juries, resulting in the need for retrials. Armstrong Jr has been wearing an ankle monitor since 2017 as a result. Since the night of the murders in 2016, Armstrong Jr has married his high-school sweetheart, Katie, and became a father. Now he will spend the rest of his life interacting with them through prison glass. During the trial, prosecutors revealed that a week before the murders, Armstrong Jr had used the murder weapon to shoot a pillow and a blanket inside his bedroom. The bullet lodged in his bedroom floor. They said he also lit a fire outside his parents' bedroom door two nights before he killed them. The evidence against Armstrong Jr did not end there; prosecutors revealed the teenager had searched for instructions on building a car bomb using his iPad. Investigators also doubted a story he told them about a masked intruder entering his home on the night of the murders. He reportedly told investigators that he saw a 6-foot-tall man in a mask flee his home on the night his parents were killed. However, he did not include that information in his initial reports, and data pulled from the home's security system showed no records of anyone entering the house on the night of the murders. Prosecutors argued that the teenager was lashing out after his parents scolded him for getting kicked out of his high school. The defence rejected that argument, and pointed to his mental health issues, which included paranoia and schizophrenia. After killing his parents, Armstrong Jr was placed in psychiatric hospitals, where a doctor testified for the defence that the teenager believed he was both a god and a devil. His defence plans to appeal the verdict. Read More Jared Bridegan: Prosecutors to announce major break in case of murdered Microsoft executive US Army soldier accused of killing his wife in Alaska faces court hearing Mississippi judge declares mistrial for two white men charged with shooting at Black FedEx worker