KUNDUZ, Afghanistan — In a time of war and corruption, when one hand grips a gun and the other opens to be greased, even the happiest of occasions can turn deadly.

On Sunday, after a wedding convoy in the northern Afghan province of Kunduz left the bride’s house for the groom’s, it was stopped at a checkpoint near a busy picnic spot. Afghan forces, the wedding participants said, asked for money — not an unusual request of newlyweds here.

In this case, the wedding party tried to bargain. The soldiers made clear it was a demand, witnesses said. Then came violence: One of the soldiers opened fire, killing two people — Mohammed Yonus, 14, and Rahimullah, 27.

Hamidullah Langar, a cousin of the groom, said the soldiers had asked for 1,000 afghanis, roughly $15. Mr. Langar handed them 200, about $3 — roughly half a day’s wages. They would not accept.