Tyler Lewis still carries the scar and the memories from the day a bullet struck him in the arm.
"You see it all the time on the news and stuff," the 17-year-old student said. "But you never think it'll happen to you."
Lewis was playing basketball at the Delaware Valley Charter School in Philadelphia last January when he and an 18-year-old female student were shot.
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"I remember just a loud sound," Lewis said. "A loud noise."
Donte Walker and Raisheem Rochwell were arrested and charged in the shooting. School officials told police that Walker, a former student at the school, was allowed to bypass security and enter the building.
Police claimed that Walker was allowed to enter the building as a "guest" and therefore didn't need to go through a metal detector like students normally do. Even if he did however, that wouldn't have mattered, according to the school's security captain John Hargraves. Hargraves told NBC10 that Walker didn't have a weapon when he went through security.
"There was no weapon when he came into the school that day," Hargraves said.
Hargraves says a teacher left a gym door open, causing a breakdown in security.
"The teacher went out there to check on the patio," Hargraves said. "He just didn't close the door."
According to Hargraves, Walker left the building through the open gym door and returned with a gun. Police say Walker planned to sell the gun to Rochwell, another student.
Investigators suspected Rochwell wanted the weapon because he feared he would be the target of an assault after school.
"If he's a target or not of a fight after school, that's still no excuse for him to have a firearm," Police Lieutenant John Stanford said. "At the end of the day, you play with a loaded gun, things will happen."
While investigators have not yet confirmed whether it was accidental or on purpose, at some point, a shot fired from the weapon. The female student was shot in the rear of her left arm. The bullet went through her bicep and then struck Lewis in the shoulder, according to investigators.
Both students were eventually treated and released.
Both Rochwell and Walker were later arrested and charged.
School officials say the teacher who left the gym door open was disciplined but they did not go into specific details.
Since the shooting, the school has enforced new security measures. All doors in the school now have alarms so that officials can detect anyone opening a door from the outside or inside.
Delaware Valley Charter School is one of 87 charter schools in Philadelphia. Philadelphia Police officers are not present in city charter schools because the schools don't fall under the Philadelphia School District's school police force. Security procedures are up to each individual charter school.