MEMPHIS, Tenn.—Two of the men arrested in connection with the killing of rapper Young Dolph had a history of violent crime, a prosecutor said Wednesday. Authorities also said that they have not yet identified a motive for the shooting. Young Dolph, whose real name was Adolph Thornton Jr., was gunned down in a daylight ambush at a popular cookie shop in Memphis on Nov. 17. Justin Johnson, who was captured Tuesday in Indiana, nearly two months after the slaying, was held in juvenile custody after he was tried at age 17 on charges of aggravated rape and aggravated robbery, Shelby County District Attorney General Amy Weirich told a news conference. He also served time for shooting three people at a bowling alley and had been arrested on state drug and weapons charges, Weirich said. Johnson, now 23, was traveling on a highway in Indiana on Tuesday when he was stopped …