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BURLESON (CBSDFW.COM) – One teenager dead, his twin brother shot, and a third teen is behind bars Sunday evening for murder. Now investigators are trying to figure out what led up to it all.

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After the suspect showed up at the Burleson Police Department with a family member to surrender and be taken into custody, detectives turned to sorting out why the teens were fighting in the first place. It’s something those close to the victims’ say they want to know as well.

Cameron Lewis

It isn’t clear why Mound Elementary School became the site of the shooting that left 17-year-old Cameron Lewis dead. Police say he and a group of teens chose the school at random for a fight that also left his twin brother Camden wounded. Friends Sydnee Griffin and Sierra Duncanson grew up with the twins.

“They were such big goofballs. Like anytime you were upset they would be there either with a smart aleck comment to cheer you up,” Griffin said.

“Or just something ridiculous,” Duncanson added.

Neither knows what led up to the fight, but the two know plenty about the brothers’ personalities, and they have their own idea.

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“I believe that they showed up here expecting just a fistfight and some words being thrown back and forth, but they were not expecting guns, or to lose their life that night,” Griffin said.

Police say the twins showed up at the school along with three others when 18-year-old Tristan Torres arrived alone in one car followed by a second car with three more people.

Investigators say Torres fired several shots hitting Cameron in the head and his brother in the foot.

“What exactly led them to meet there to fight is stuff that we’re still trying to figure out. That’s the why that we just don’t know yet,” Burleson Police Chief Billy Cordell said.

Torres turned himself in and led police to the murder weapon. As the investigation continues, many in the community remain shocked that this could happen here.

“We’ve enjoyed a great low crime rate in Burleson, but you know we’re not immune to anything. No city is immune to anything,” Cordell said.

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Police say the witnesses are cooperating with detectives who will meet Monday with the District Attorney’s office.