Why did Zhou Weiguo's arm break in the TV series "New Snow Leopard"?

During the Japanese siege, the situation was very tense. The Japanese army pursued a large area in the dark, and the Eighth Route Army was not many. After several victories, it was exhausted. I was having a rest when I found that the Japanese had pushed me up again, so I quickly retreated. However, because there are ghosts everywhere, there is really nowhere to escape. In desperation, Zhou Weiguo found a cliff (it doesn't seem to be called a cliff, but it's quite short, five or six stories high), so he quickly directed the team members to climb up with the help of ropes. There is no devil on it. If he goes up from the top, it may turn things around. However, in the middle, the Japanese army is approaching, but Zhou Weiguo and others haven't gone up yet. Zhou Weiguo and several comrades around him, as well as those who have climbed up, used machine guns as cover to attract the fire of the devils, so that those comrades who had not climbed up could hold on tight. But there are always comrades who were shot and killed by random guns in the process of going to bed. Zhou Weiguo nasty, crazy shooting, cooperate with the comrades above, to buy a little time for large forces, but forget that they haven't go up. The devils became more and more arrogant, and finally Zhou Weiguo was the only one who didn't go up. At this time, the intensive firepower of the Japanese can no longer stop, and Zhou Weiguo is trapped there and can't get on. Rola Chen looked terrible up there and shouted "Guo Wei" anxiously, but there was nothing he could do. However, in such a tense situation, Zhou Weiguo suddenly found that the bullets were used up, and his heart was dark. He looked around, ran away quickly and rushed to the cliff (he had been attracting Japanese artillery fire). However, just a few steps later, Zhou Weiguo was knocked down by the Japanese gunfire. The arm is bloody. It was this injury that cost him his left arm.

See episode 28 of The Strong Years of Snow Leopard for details.