I created a mission with the editor just to explore the island. I had one friendly AI with me. I shot him in the leg a couple times. I thought he would be unable to keep standing, but he just stood there like nothing happened. After 6 shots, all in the leg, he fell to the ground and died.

There are injuries in which the player can't stand up anymore. I thought the AI would have the same damage model and shooting someone in the leg multiple times would be an instance of this.