The propeller plane found itself in trouble shortly after take-off from the Atterheide airport in Osnabrück on Thursday morning, the Neue Osnabrücke Zeitung (NOZ) reports.
One of the two engines had malfunctioned, leading the pilot to scramble to find a flat area to land on.
He spotted a former army barracks and took the plane down as smoothly as he could, trying to ensure a controlled crash-landing.
But the jet was completely destroyed by the impact, leaving two of the four people on board lightly injured and the other two so seriously wounded they couldn't leave the stricken vehicle.
Hassanien Salman, a 34-year-old Iraqi veterinarian living in a refugee shelter on the same former barracks, heard the crash as he was taking a shower.
Hassanien Salman. Photo: DPA
When he took a look outside and saw the smoking wreckage, he threw on a pair of boxer shorts and a T-shirt and rushed to the crash site.
Two men had already freed themselves, Salman said. But he could smell gasoline and see flames and the men in the front seats were badly injured and stuck tight.
Together with another refugee from the shelter who had arrived shortly afterwards, he was able to extinguish the fire and pull the men from danger.
Although he is "only a vet" Salman told NOZ, he was able to recognize the severe head wounds one of the men had and give him emergency treatment.
Emergency crews turned up at the site soon after and took over care of the injured, all of whom survived.
"A lot of people had a lot of luck today," a police spokesperson said.