How did the boy from district 3 died?

Answer 1

the boy from district 3 was killed by Cato. Once, Katniss blew up all the Career supplies by triggering the explosions the boy from district 3 had set up around the Career's campsite, Cato was so angry that he channeled all his anger at the boy from district 3, since he was the one that set up the explosions and Cato twisted his neck into a headlock and snapped his neck.

Answer 2

In the book it never says how he dies, it just says that he dies in the bloodbath. In the movie the boy hides in the cornucopia for a little bit then he runs out and gets stabbed in the stomach with an axe by Cato. Poor guy.

Answer 3

The boy from District 3 was supposed to help guard the Career's supplies by rewiring the mines from the circular platforms at the beginning. When Katniss destroys the supplies, the career's come back to their base camp to discover the supplies had been blown up. Cato is in a rage about the supplies so he breaks the District 3 boy's neck. Katniss claims she "can see Cato's muscles ripple" as he breaks the boy's neck.

Answer 4

The boy from 3 died when Cato swung his head around when he was angry about Katniss using the mines that the boy set to blow up the food.