Apparently, this actually happened. 😱 https://t.co/60KaXWo7YT— hilzoy (@hilzoy) April 13, 2020
Here's the Wikipedia page for the Imber Friendly Fire Incident:
On 13 April 1942, the weather was hazy, and six Royal Air Force (RAF) Hawker Hurricanes from No. 175 Squadron RAF and six Supermarine Spitfires from No. 234 Squadron RAF were being used for a demonstration of tactical airpower at Imber, a British Army training ground on Salisbury Plain in Wiltshire. The event was a dress rehearsal for an upcoming visit by Winston Churchill and General George Marshall, Chief of Staff of the United States Army and was attended by a number of military personnel. The Spitfires overflew followed by the Hurricanes. Five of the Hurricanes hit the correct targets: several armoured vehicles and mock tanks. The pilot of the sixth Hurricane opened fire at the spectators before continuing with the demonstration. Casualties were 25 military personnel killed and 71 wounded.And here's the general Wikipedia page for Friendly Fire Incidents.