Why does the boy from district 3 shock the gamemakers?

Answer 1

He was an overall boring tribute in the training and the interviews, so they expected him to die early. District 3 produces electronics, so the boy from District 3 was able to make mines (explosives) under the food pile that would explode on pressure if anyone were to try to steal food. He made the mines by digging up parts of the metal plates that lifted the tributes up from under ground at the beginning of the games and using the pieces to make bombs. The plates deactivate after 60 seconds, but somehow the boy was able to reactivate them. This was most likely frowned upon by the gamemakers considering Haymitch did a similar thing in his games and was punished for it.

Answer 2

He shot an arrow

Answer 3

He died