Beech Baron destroyed after landing gear retracts during takeoff roll

On November 9, 2019, at 1024 eastern daylight time, a Beech BE55, N686DR, was substantially damaged when it was involved in an accident near Griffin, Georgia. The commercial pilot and four passengers were not injured. The airplane was being operated Part 91 personal flight. The pilot reported that he was giving rides in his airplane as part of a "patient appreciation" day, and that the accident flight was his fifth flight of the morning. After the passengers boarded, the pilot taxied to runway 14 and completed the before-takeoff checklist, then applied full power for takeoff. He reported that everything appeared normal during the takeoff roll, but, as the airplane approached 70 knots, about one third of the way down the runway, the landing gear suddenly retracted, and the airplane skidded off the right side of the runway before coming to rest partially on the grass and runway pavement. Examination of the airplane by an FAA inspector revealed that the airplane sustained substantial damage to the underside of the fuselage.
Following the accident, the pilot noticed that the landing gear handle was in the up position; he reported that it may have been accidentally bumped by one of the passengers as they got into the airplane. A subsequent follow-up examination of the airplane and its landing gear system revealed that the gear handle operated normally, and the landing gear functioned as designed. No anomalies were discovered with the system that would have precluded normal landing gear operation. Maintenance was performed on the landing gear handle on January 19, 2018, at an airframe total time of 3,896 hours, because the landing gear control handle was loose due to a selector handle spring retainer irregularity. The landing gear handle was repaired, and functionality was verified. There were no additional maintenance irregularities noted with the system during subsequent maintenance and the pilot reported no issues with the landing gear since the maintenance was performed 22 months before the accident.
The airplane's "initial" checklist includes a line item stating "gear lever -down." According to the airplane flight manual landing gear systems description, the airplane was equipped with a safety switch to prevent inadvertent retraction of the landing gear on the ground; a main strut safety switch opens the control circuit when the strut is compressed. A caution note stated, "Never rely on the safety switch to keep the gear down during taxi or on takeoff, landing roll, or in a static position. Always make certain that the landing gear switch is in the down position during these operations."
The NTSB determined the probable cause of this accident to be the pilot's failure to ensure that the airplane was properly configured for takeoff, which resulted in the inadvertent retraction of the landing gear during the takeoff roll and the airplane's subsequent runway excursion.