Question regarding the El-melloi Case Files series (potential spoilers)

At the end of the mystic eye train arc, Gray unleashes her NP and Karabo dies. What i dont get is why Karabo suddenly dies. It looked like he was fine in the previous chapter? He got kicked by Faker but he was able to stand up and talk afterwards, and it didnt look like he was badly injured at all (no coughing blood, etc). Then after Gray uses her NP, suddenly he's dead. I dont understand what happened.