On October 10, 2015, at 1400 eastern daylight time, a Cessna 172S, N5295Y, was substantially damaged after a loss of control during a low altitude maneuver near Seville, Florida. The commercial pilot and pilot-rated passenger sustained serious injuries, and the rear seated passenger was fatally injured. The airplane was registered to Mike Bravo LLC., and operated under the provisions of 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions were reported near the accident site about the time of the accident, and no flight plan was filed. The local flight originated from Daytona Beach International Airport (DAB), Daytona, Florida at 1300.According to the pilot, while flying about 600-650 feet above ground level (agl) at a speed of 75 knots with 20° of flaps, the airplane suddenly "fell out from under" him. The airplane lost 300-350 feet of altitude within a few seconds. He applied full power to recover the altitude but the airplane continued to "sink." He maneuvered the airplane towards a clearing to avoid trees, lost control, and collided with the ground. According to the operator of the airplane, the pilot called twice on the day of the accident. He initially called to apologize for the accident and in the evening, he called to explain what happened earlier that day. The pilot stated earlier that day he brought one passenger and then picked up another. He said that the intent of the flight was to "drop boxes" south of Lake Crescent, at a campsite managed by St. Johns River Water Management District. The pilot said he was aware that dropping objects out of the airplane was prohibited, but assured the operator that he had coordinated with the people on the ground to stay out of the way when the items were dropped. When the pilot reached the campsite, he descended to an altitude between 300 and 600 feet agl, configured the airplane with 20° of flaps, and slowed it to 75 knots. After successfully dropping several boxes, and during the final drop, the airplane encountered a downdraft and lost altitude. The pilot attempted to recover, but the airplane subsequently impacted trees and terrain. Examination of the airframe and engine by a Federal Aviation Administration (FAA) inspector revealed no anomalies that would have precluded normal operation. The 1453 weather conditions reported at DAB included scattered, towering cumulus clouds at 3,500 feet, scattered clouds at 5,000 feet, scattered clouds at 7,500 feet and a broken ceiling at 25,000 feet, and winds from 060° at 6 knots. Additionally, towering cumulus clouds were noted to the south, and cumulonimbus clouds were noted in the distance to the east, southwest, and northwest of the airport. DAB was located 23 nautical miles southeast of the accident site. The National Weather Service National Radar Mosaic for the period depicted isolated echoes associated with rain showers approximately 5 miles west and 10 miles southwest of the accident site, near Georgetown and Aster, Florida on the ends of Lake George, with a small isolated intense area of echoes immediately east of DAB at the time. A North American Mesoscale Model sounding for the area of the accident site suggested the potential for strong low-level thermal activity and an unstable atmosphere, with expected clouds developing near 3,000 feet agl. The sounding did not depict the presence of low-level turbulence or windshear.