On March 20, 2017, about 0405 mountain daylight time, a Swearingen SA226TC, N158WA, was substantially damaged due to foreign object damage to the airplane's fuselage during initial takeoff/climb from Boise Air Terminal/Gowen Field (BOI), Boise, Idaho. The airline transport pilot was not injured. The airplane was registered to and operated by Western Airlines LC of Boise as a 14 Code of Federal Regulations Part 91 positioning flight. Visual meteorological conditions prevailed at the time, and an instrument flight rules flight plan was filed and active. The flight was originating at the time and destined for Salt Lake International Airport (SLC), Salt Lake City, Utah. In a written statement submitted to the National Transportation Safety Board investigator-in-charge, the pilot reported that prior to departing on the repositioning flight, he reviewed the maintenance data for the airplane (the Can) and found everything to be up to date. The subsequent preflight inspections, inclusive of the interior and exterior of the airplane revealed no anomalies. The pilot stated that at 0400 he called BOI ground control, obtained taxi clearance, and taxied to runway 10L where he began the takeoff roll. The pilot reported that everything was normal, rotated at 105 knots; shortly thereafter he heard a "pop", followed by a vibration. Thinking that he had a blown tire, he waited a few seconds to see if the frequency of the vibration would change as the tire rotation slowed. However, the vibration remained the same, which led him to think that there might be an issue with the propeller. The pilot radioed the BOI tower controller, advised him of his intension to return to the airport, and was instructed to turn right for Runway 10L. The pilot stated that on the downwind leg he thought there might be a problem with a propeller. However, after he inspected both propeller spinners to determine which propeller might be damaged, he determined that both were running smooth. The pilot further stated that as he had no indication as to which propeller was damaged and the vibration was light and not changing, he elected not to shut the engine down. The pilot then landed uneventfully, taxied to parking, and shut the right engine down first. The pilot then shut the left engine down. During the last few rotations of the propeller he observed the spinner wobble slightly; he then noticed that the tip of one of the blades was missing. The pilot stated that after having exited the airplane he observed that about four inches of one of the propeller blade tips was missing, as well as having observed two holes in the fuselage, [both caused by pieces of the propeller blade tip]. About 10 minutes later airport operations personnel delivered another piece of the propeller [blade], and what appeared to be the blade of a screwdriver and two pieces of a screwdriver handle. A further examination of the airplane revealed a third hole in the fuselage further back [of the left] wing root just below the window. During a postaccident inspection of the airplane, a Federal Aviation Administration aviation safety inspector reported that maintenance had been performed on the airplane prior to the flight, and that the mechanic was called away from the task he was performing prior to it being completed. The inspector stated that a screwdriver was left on the nose of the airplane under the windshield wiper and out of sight of the pilot. Subsequently, on takeoff roll the screwdriver became dislodged and impacted the left propeller; remnants of two pieces of a propeller blade were found to have penetrated the left side fuselage and came to rest inside the cabin of the airplane. The screwdriver was subsequently located lying on the surface of the departure runway.