Perhaps, as the pig was small, and, as they were doubtless hungry, they did not wish their capture to be widely known.

At any rate, they came cautiously up a ravine and had not been noticed until their heads rose above it.
They saw the two Frenchmen just about as soon as they were seen.

The third man, whose arms were free, immediately presented his piece and pulled the trigger.

Fortunately it missed fire.

If it had gone off it might have attracted the attention of the Russian outposts, investigations would have been instituted, and all chance of passing the lines there would have been over.
At the same time he pulled the trigger he fell like a log.