Mississippi teen Carly Gregg seen on phone seconds after allegedly killing her mother, Ashley Smylie

A chilling video shows a Mississippi teenager calmly walking into her home to shoot her mother, then sending flirty text messages to lure her stepfather to her home, and shooting him as well, prosecutors say.

Carly Gregg, 15, is currently on trial for allegedly killing her mother, Ashley Smylie, a high school teacher, and then shooting her stepfather, Heath Smylie, in their Brandon, Mississippi, home in March after learning of his “secret life” with drugs.

Alarming surveillance video presented in court Tuesday shows the baby-faced teenager moving awkwardly through the house — allegedly holding a gun behind her back shortly before opening fire.

Gregg, wearing a Nirvana T-shirt, was filmed disappearing off-camera into his mother’s bedroom seconds before three gunshots rang out, followed by Smylie’s piercing screams, according to the clip obtained by Law & Crime.

The teenager then returned to the kitchen about 10 seconds later, still allegedly holding the gun behind her back.

Prosecutors said Gregg faced the camera the entire time in an attempt to hide the weapon, which was later identified as a .357 Magnum pistol.

Once back in the camera’s view, Gregg could be seen grabbing her mother’s phone from the kitchen counter and calmly sitting down on a stool as her two dogs stood next to her.

Prosecutors say Gregg then casually sent several text messages, including one to his stepfather to lure him to his home.

“When will you be home, honey?” the message sent to Heath read.

When Heath returned home a short time later, Gregg allegedly shot him in the shoulder before he could wrestle the gun from him, the court heard.

Prosecutors said the teenager also allegedly sent a text message to a friend asking her to come over because there was an “emergency.”

“Have you ever seen a dead body? My mother is in there,” Gregg allegedly asked him when he arrived home.

Gregg allegedly carried out the shootings just hours after a friend apparently informed his mother — who worked as a math teacher at her daughter’s Northwest Rankin High School — about the teen’s marijuana use.

When the couple returned home from school that day, the mother began searching Gregg’s room and discovered a stash of vape pens, the court heard.

“According to testimony from a friend, he was so concerned about Carly’s marijuana use, so concerned about her being high and so concerned about her having these disposable phones, which (Carly’s) mother didn’t know about, that he felt compelled to tell Ms. Ashley Smylie that day,” Rankin County Assistant Prosecutor Kathryn Newman said earlier in the trial.

Psychiatrist Dr. Andrew Clark testified that the teenager was experiencing a mental health crisis on the day of the shooting.

He said the teenager had severe mood swings, heard voices and had dissociative issues, which were made worse by her medication.

“And then her mother finds out she’s smoking marijuana,” Clark told the court. “For Carly, in particular, she was so attached to her mother’s approval, so for her, it was a crisis.”

Meanwhile, Gregg’s stepfather testified Tuesday that the teenager — whom he described as a “sweet little girl” — had no memory of the shooting.

“I’ve never seen anyone like that, even in the movies, she wasn’t herself and I don’t think she even recognized me,” Heath said, adding that he and Gregg still talk daily and their relationship is “good.”

Gregg was charged with murder, attempted murder and tampering with evidence.

She refused a plea deal and is continuing her defense on the grounds of insanity.

The teenager faces life in prison for the murder, plus 30 years to life in prison for the other charges if convicted.