What does Katniss do when the careers come to rest under the tree in which she was hiding?

Rue, the little girl from another district, was helping Katniss from another tree. Rue pointed out a Tracker Jacker nest below her. Tracker Jackers are like very vicious bees. But instead of just stinging you, they inject venom inside you which causes hallucinations, sometimes makes you go unconscious and in the worst situation it can kill you. Rue pointed out the nest because she didn't want Katniss to get stung. But Katniss really wanted to get rid of the Careers, so she took a knife- risking her life because of the Tracker Jacker venom- and cut the branch that the nest was hanging from, causing it to fall on the careers. That made them run away and killed one of the careers.