In March of 1945, New Zealand pilot William Arthur Kalka was returning to his home airbase in Volkel. Shortly before reaching his destination, his plane was shot down over Nijmegen by German anti-aircraft gunfire. The pilot, who during the war had already intercepted eight V1 flying bombs in the air before they could strike, prepared for one last act of heroism. His aircraft had been hit while flying over a populated area, which would result in a major disaster if it were to crash immediately. So, Kalka stayed with the plane in an effort to keep it airborne until it had moved away from the populated area. He succeeded but paid a heavy price for this heroic act. As a result of waiting so long, the plane was already quite low when he jumped from the cockpit, too low for the parachute to open properly. Together with his plane, Kalka landed in the River Maas, where his heavy equipment dragged him to the bottom.

Given that this had taken place on a Sunday afternoon, just as mass in the nearby church in Balgoij had ended, the churchgoers saw the plane crash and the young pilot disappear into the river. Only 21-year-old Riet Jansen from Nijmegen, who happened to be cycling along the dike, came to his aid. She dove into the water and tried to pull the young man up, but in vain. Disappointed and shocked, she returned to the bank, only to find that someone had stolen her bicycle.

After the war, the entire Jansen family was invited to Huize St. Anna on the Groesbeekseweg, the building that was then serving as the temporary city hall of Nijmegen and the headquarters of the military government. Here, Riet received a letter of gratitude and a brand-new British bicycle on behalf of the High Commissioner of New Zealand.

The grave of William Arthur Kalka is located at the Commonwealth War Cemetery Uden in the province of Noord-Brabant.

Today, an information plaque recalls the actions of these two brave people.