An off-duty security guard from Newcastle was convicted of murder Friday in the 2024 killing of a teenage boy he shot seven times outside a Big 5 Sporting Goods store in Renton. A King County Superior Court jury in Kent deliberated for two days before delivering its unanimous verdict, finding 52-year-old Aaron Myers guilty of second-degree assault and second-degree murder.   After the verdict, Judge Nikole Hecklinger ordered that Myers be returned to jail custody as he awaits sentencing on July 21. He faces between 10 and 18 years imprisonment for the two convictions, plus an additional 10 years for a firearm enhancement. Myers has been under electronic home monitoring since July 2024, when he posted bond on his $2 million bail and was released from jail. He maintained a stoic expression Friday morning as the presiding juror announced the verdict. He eventually turned and embraced his wife, who wept as two sheriff’s deputies entered the courtroom and approached them.…