The King County, Washington, Prosecuting Attorney’s Office has charged a man with second-degree murder and assault, both felony counts, for allegedly shooting a teen he thought was holding a gun and who he believed was about to rob a sporting goods store.

Aaron Brown Myers, 51, told police he believed the 17-year-old victim had a gun and was going to rob a Big 5 Sporting Goods store in the Seattle suburb of Renton last Wednesday as the teen headed toward the retailer with two others, according to court documents filed by the prosecutor, Leesa Manion.

The boy was holding an airsoft gun, according to a police affidavit. An airsoft gun is a replica firearm that shoots low-power, nonmetallic pellets.

The two teens who were with the victim told police they were going to the sporting goods store to either return or exchange the airsoft gun because it was malfunctioning, the affidavit said.

Myers was charged on Monday with the two felony charges and is scheduled to be arraigned on June 24, according to the King County Prosecutor’s Office. Myers is currently being held on a $2 million bond, according to the office.

“The investigation revealed that the victim and two other 17-year-olds were walking toward a store to return a handgun-style BB gun when the armed suspect got out of his vehicle and confronted the trio,” according to the filing obtained by ABC News. “There was an altercation that turned physical, and the suspect allegedly shot the victim multiple times.”

Myers told police he works as an armed security guard elsewhere, and he had just gotten off work and was waiting in his car in a parking lot as his son attended martial arts classes nearby, according to the police affidavit.

“Myers indicated that he conducted ‘overwatch’ at the location as he has seen numerous crimes occur in the parking lot in the past,” the affidavit read.

Reports do not show that Myers was authorized to guard the area.

Myers saw three teens approach the Big 5 Sporting Goods store with what he thought were handguns and believed they were going to rob the store, according to the affidavit. He further stated that he felt he did not have time to call 911 and that he “had a duty to act to stop the individuals from hurting someone innocent, and to protect his son,” per the court filing.

Myers, who was armed with a registered semiautomatic pistol, told police he approached the teens with his gun out and told them to put their hands in the air, but no one complied, the police affidavit said. He then fired multiple rounds at the victim because he thought the teen was reaching into the waistband of his pants for what Myers believed was a gun and that the teen “was going to kill him,” according to the filing.

The 17-year-old, whose name was redacted from court records because he’s a minor, was pronounced dead at the scene by first responders, the filing said. Myers was immediately detained and taken into custody.

“Mr. Myers and his family are devastated by this tragedy and the fact that it resulted in the loss of a young man’s life. On the evening in question Mr. Myers sincerely believed that he was witnessing the beginning of an armed robbery,” Myers’ attorney said in a statement to ABC News. “Unfortunately, during the confrontation Mr. Myers became in fear for his own life and fired his duty weapon to defend himself.”

The two surviving teens said they previously used the airsoft guns to shoot in the woods and wanted help from the store with their replica firearms, which were malfunctioning, according to the affidavit.

Investigators stated in their report that surveillance footage of the incident appeared to contradict some of Myers’ statements.

The surveillance footage also shows Myers quickly approaching the teens in the parking lot, the filing said. After he forces one teen to the ground and straddles him, he points his gun at another, per the affidavit.

The teen with the gun pointed at him had his hands up but lowered one of his hands toward his waist, at which point Myers is seen firing his weapon multiple times, according to the filing.

“Based off these facts I believe there is Probable Cause to charge Aaron B Myers … with the crime of Murder in the second degree,” according to the police officer involved, the court filing said. “Myers actions of discharging his firearm, without premeditation, caused the death of another person.”

In response to an ABC News’ request for comment, the deceased boy’s father said he was too distraught to speak about the incident.

Renton, Washington, police told ABC News that surveillance footage of the incident will not be publicly available until their investigation is complete.