The narrator noticed that there was a change in Kari’s behaviour while they were trying to save the young boy. What was the change?

Generally, Kari was slow and ponderous, but the narrator noticed that in an attempt to save the young boy’s life. Kari became very fast and darted down like a hawk. He quickly came halfway into the water. Kari took action very fast to make all possible attempts to save the life of the boy.