Why didn't James believe Beckham was alive in The Hurt Locker?

What's the reason the boy looking like Beckham was killed?

The boy looking like Beckham was killed because it was a manner in which the terrorists planted bombs inside dead bodies so that when people came to collect the bodies, they would detonate - thus killing even more people.

The boy was a random boy and was not killed because he looked like Beckham. So there is no linkage there.

Who killed the boy looking like Beckham?

Terrorists.

Why was he covered with an unexploded bomb?

See answer to your first question above. If you have seen the film No Man's Land, a similar technique is used which also becomes the focal plot point of that film.

Why James didn't believe Beckham was alive?

I believe that James hadn't seen Beckham for quite sometime and the dead boy looked similar to Beckham. Added to this, being in a war zone can be quite stressful and hence it is only normal that your mind makes you be on an edge and really alert to your surroundings. Hence even a small suspicion is blown out of proportion. (Guilty unless proven innocent in this case)

First off, the Hurt locker is a very good film that actually does some justice to those who served during that conflict. The movie has a lot of accuracy in regards to Iraq, the war and our troops- basically, their struggle in that atmosphere. Very few movies about Iraq are this good with the exception of American Sniper and a few others. Anyways, I agree this is a confusing aspect of the movie and for so long I figured the insurgents had placed another child there to confuse the main character but my opinion has since changed. In my opinion (and that is what it all comes down to), Beckham- the little Iraqi boy who sells DVD's on the base- was never actually killed. Confusion and combat stress go hand and hand, causing sergeant James to make erroneous and reckless decisions (lets face it, he was kind of reckless from the beginning). The likelihood that another boy could look and sound equally like Beckham is unlikely. So my thoughts are that insanity and stress were getting the best of the main character. His relationship and compassion for the boy, while noble and heartwarming, was jeopardizing his relationship and the safety of himself and his troops. So there you have it, insanity and mistaken identity were the culprits in this one. Sorry for the long response but I love this movie and I was over there in northern Iraq, Mosul to be exact, once too. Lastly, It is also worth noting that sergeant James is a father too (as we see him playing with his young son at the end of the film) and this could be a major factor in his compassion with the Iraqi boy. Perhaps it made it more personal for him.