A German engineer abducted in Afghanistan last month died of gunshot wounds, the foreign ministry said Thursday after an autopsy of the body in Cologne, according to dpa. The 44-year-old was one of two German engineers kidnapped on July 18 in the central province of Maidan Wardak by a local Taliban group with an apparent criminal background. Afghan police found his bullet-riddled body at the side of a road four days later and it was flown back to Germany on July 25 for an autopsy. German media reports said the man was a diabetic and there was speculation he was killed when his abductors found he could not keep up with them while they were marching him through the mountains. Foreign ministry spokesman Martin Jaeger said the autopsy showed the construction engineer had collapsed but was still alive when his captors turned their guns on him. "After he collapsed two shots were fired at the victim while he was still alive," Jaeger said. "Four more bullets were fired at the body after death set in." "This crime must not be allowed to go unpunished," German Foreign Minister Frank-Walter Steinmeier said in Accra during a visit to Ghana as part of a West African tour. "The final hours were nothing short of martyrdom for the victim. His abductors drove him to death, finally putting an end to his life in a criminal manner." Steinmeier said efforts now had to concentrate on obtaining the release of the other hostage, who is reported to suffer from high blood pressure and to need regular medication. Al Jazeera television broadcast a video on Tuesday showing the man against a rocky background in a hilly area. There was no sound on the video, but the channel said the hostage, Rudolf B., had urged the German and US governments to "withdraw their troops from Afghanistan" and to help him return to his family. The German Foreign Ministry said the video was a deliberate attempt to intimidate. German Chancellor Angela Merkel has said Berlin will not give in to the kidnappers' demands. The dead man, identified only as Ruediger D, is survived by his wife and school-aged son. He was buried on Wednesday in a ceremony attended by close family members in Neumuenster in the northern state of Schleswig-Holstein.