The teenager accused of fatally stabbing Austin Metcalf and leaving him to die in his twin brother’s arms at a high school track meet allegedly admitted to the senseless killing — but claimed it was in self defense.

“I’m not alleged, I did it,” 17-year-old Karmelo Anthony chillingly told police in Frisco, Texas as he was being arrested at Kuykendall Stadium, according to an arrest warrant obtained by NBC DFW.

The horrific stabbing was sparked when Anthony, who was sitting under another team’s pop up tent as it rained Wednesday morning, was asked by Metcalf to move — and Anthony refused, according to the arrest report.

High school junior, Austin Metcalf, was fatally stabbed in the heart. @Jeff Metcalf/Facebook

Karmelo Anthony allegedly told police, “I’m not alleged, I did it” — but has claimed the stabbing was in self-defense. Collin County

Anthony then unzipped a bag, reached inside and told Metcalf, who he’d never met before, “Touch me and see what happens,” a witness told police, according to the document.

Moments later, Metcalf “grabbed Anthony to tell him to move and Anthony pulled out … a black knife and stabbed Austin once in the chest,” police said.

Anthony ran away before he was chased down and arrested.

“I was protecting myself,” Anthony allegedly told cops “He put his hands on me.”

He also then asked cops what constitutes self-defense and whether or not Metcalf would be ok, according to the report.

Metcalf, a junior at Memorial High School outside Dallas, suffered a stab wound to the heart and died in the arms of his identical twin brother, Hunter.

Metcalf died in his twin brother’s arms. Jeff Metcalf / Facebook

Austin Metcalf with his father, Jeff Metcalf. GoFundMe

“It really was under 30 seconds, this altercation,” Hunter told WFAA in an emotional interview.. “I never met this kid in my life.

“My brother stepped in and said, ‘You need to move,’” Hunter added, “And [Anthony’s] like, ‘Make me move.’

“All of the sudden, he grabbed his backpack,” the brother said.