Given the following context:  Piper reported that as he was leaving Exchange Buildings to return to Houndsditch he saw a man acting suspiciously in the shadows of the cul-de-sac. As the policeman approached him, the man walked away; Piper later described him as being approximately 5 feet 7 inches (1.70 m), pale and fair-haired. When Piper reached Houndsditch he saw two policemen from the adjoining beats—constables Woodhams and Choate—who watched 120 Houndsditch and 11 Exchange Buildings while Piper went to the nearby Bishopsgate Police Station to report. By 11:30 seven uniformed and two plain clothes policemen had gathered in the locality, each armed with his wooden truncheon. Sergeant Bentley from Bishopsgate police station knocked at number 11, unaware that Piper had already done so, which alerted the gang. The door was answered by Gardstein, who made no response when Bentley asked if anyone was working there. Bentley asked him to fetch someone who spoke English; Gardstein left the door half-closed and disappeared inside. Bentley entered the hall with Sergeant Bryant and Constable Woodhams; as they could see the bottom of his trouser legs, they soon realised that someone was watching them from the stairs. The police asked the man if they could step into the back of the property, and he agreed. As Bentley moved forward, the back door opened and one of the gang exited, firing from a pistol as he did so; the man on the stairs also began firing. Bentley was shot in the shoulder and the neck—the second round severing his spine. Bryant was shot in the arm and chest and Woodhams was wounded in the leg, which broke his femur; both collapsed. Although they survived, neither Bryant or Woodhams fully recovered from their injuries.As the gang exited the property and made to escape up the cul-de-sac, other police intervened. Sergeant Charles Tucker from Bishopsgate police station was hit twice, once in the hip and once in the heart by Peters: he died instantly. Choate grabbed Gardstein and wrestled for his gun, but the Russian managed to shoot him...  answer the following question:  What was the full name of the passerby who accosted Gardstein and his accomplices??
A:
Isaac Levy