In "The Interlopers," when the men first spot each other, why don't they immediately kill one another?

The feud between the Gradwitz and Znaeym families stretches back three generations and is inherited by the two main characters, Ulrich and Georg, who continue to quarrel over a narrow strip of precipitous land that the Gradwitz family possesses.
On a wintry night, Ulrich von Gradwitz patrols the disputed territory with his men in hopes of discovering Georg Znaeym poaching on his land. Ulrich von Gradwitz plans on killing Georg the instant he runs into him. However, when Ulrich and Georg cross paths alone in the forest, both men hesitate and do not immediately shoot their rifles.
The narrator mentions that both men uphold a moral code, which prevents them from murdering an enemy in cold blood. Both Ulrich and Georg view themselves as civil men who adhere to the moral code and will not kill each other unless they are immediately threatened or formally challenged, which is why both men refrain from firing their weapons. A massive tree falls on both of them during their moment of hesitation, which further prevents them from killing each other.

Georg and Ulrich's families have been involved in a long, bitter feud that stretches back for generations. So, when they confront each other one cold winter's night in the forest, it seems that bloodshed is very much in the cards. Both men are armed with hunting rifles, which merely adds to the tension and sense of foreboding in the air.
Yet to our surprise, neither man tries to kill the other. For despite their mutual loathing, Georg and Ulrich still consider themselves civilized, and the moral code to which they both adhere strongly prohibits the killing of another human being in cold blood. To be sure, lethal force can indeed be used, but only under certain circumstances. The moral code dictates that it is acceptable to shoot and kill one's neighbor, but only to defend one's property or as a means of restoring injured honor, as in a duel.