date. Twice before taking off at 4:00 a.m., 16 June, Zeamer rejected orders to add to the mission a reconnaissance of Buka airdrome, located off Bougainville's northern tip. The assigned mapping would be hazardous enough, he felt, without prematurely alerting the airbase of their presence. Early arrival at the initial mapping point meant a half-hour delay in starting the mapping run; the sun was not high enough for the light necessary for topographic relief. The delay prompted Zeamer to ask his aircrew's opinion of the Buka recon. All supported going ahead with it, considering their proximity. As a result, Zeamer circled to come over Buka from the northeast, so as to continue into the mapping run down Bougainville's west coast. Contemporary accounts indicate the aircrew counting around 50 enemy aircraft on either side of the airfield, with crew statements given in support of Zeamer's Medal of Honor reporting 17 or 18 Japanese fighters either taxiing or taking off, as Old 666 flew over the island. These were Japanese Navy Model 22 Zeroes of 251 Kukutai (Air Squadron), most of which were usually based at Rabaul, New Britain. They had moved to Buka airdrome the previous day for a planned 16 June attack on Guadalcanal. Zeamer began the mapping run, hoping to complete it before the Zeros could reach their mapping altitude at . Shortly before its completion, ineffectual passes from below were followed by a handful of Zeros enclosing the B-17 from below in a coordinated attack, two approaching from the rear and three fanned across the front. The combination left Zeamer unable to execute his usual defensive air tactic of turning inside the line of fire of enemy aircraft attacking from the front. Such a maneuver, in this case, would expose his B-17's belly to the Zeros attacking from the front. Aware of their position over Empress Augusta Bay, the primary mapping objective, Zeamer held the course, hoping to fight it out. This first attack proved fatal for bombardier 2nd Lt. Joseph Sarnoski, who was mortally wounded by a 20mm shell hit, which also badly injured the navigator, 1st Lt. Ruby Johnston. Another 20mm struck the side of the cockpit behind the pilots, sending shrapnel into the legs of Sgt. Johnny Able, the assistant flight engineer substituting that day as the top turret gunner. The shell also struck the oxygen and hydraulic lines behind the cockpit, starting a fire.