I managed to find some info about this specific incident. Prior to this test, bouncing bombs had been successfully implemented to destroy German dams and a new, smaller bomb was in development for use in the Pacific against Japanese trade vessels. After this happened, the US military lost interest in the concept and the war would be won only a few months later.

The type of bomb was not the large ‘UPKEEP’ used so successfully by Lancaster bombers over the Rhur dams, but the smaller ‘HIGHBALL’, eventually dropped by the Mosquito. The ‘HIGHBALL’was designed to be used against Japanese shipping in the Pacific, but constant problems delayed the programme and these problems were not cured before the end of the war.

In January 1945, a USAAF A-26B Invader was adapted at the Vickers experimental facility at Foxwarren to carry two Highball inert weapons almost completely enclosed in the bomb bay, using parts from a Mosquito conversion. After brief flight testing in the UK, the kit was sent to Wright Field and installed in an A-26C Invader. Twenty-five inert Highball weapons, renamed "Speedee" bombs, were also sent for use in the USAAF trials. Drop tests were carried out over the sea near Eglin AFB, Florida.

On several drops, the A-26, which flew these experimental missions codenamed Speedee, was very low (under 10 feet) and on the 28th April 1945, the bomb hit the tail with fatal consequences, as can be seen below. American interest in the weapon then faded; there was only one converted A-26 Invader. The A-26 conversion was performed at the Vickers works at Weybridge.

http://napoleon130.tripod.com/id725.html