the student is Shin's Brother. They all planned to kidnap Yeonwoo while Shin is on his way to his father. However, Shin will not go and will find out that his sunbae is missing. Shin works with some alphas and while investigating what happened. Limping guy did hurt Yeonwoo ( he broke his bones etc) but yeonwoo fought and got away. Then, the kidnappers found out that Shin is still in Korea. Shin and his crew was able to locate the limping guy (the one who tried to mark yeonwoo before) and Shin him in front other alphas ( they have like club where the dominant alphas gather around). I think in their world, awakened alphas can do so if someone hurts their omega stuff like that.