Quote: "In a sign of protest, the fortress's Commandant Michał Wołodyjowski and Major Hejking blew up the castle's remaining gunpowder, killing themselves along with 800 defenders." 
 This is probably a silly joke. Wołodyjowski and Ketling (not Hejting) are fictional characters from Sienkiewicz's novel "Mr. Wołodyjowski". In than novel they indeed blow themselves up with part of the castle after the surrender.".