Even though we won't see Super 8 until June 10, we know there's a huge alien threat in store for us. At the beginning of the film, the characters don't yet know about it. But they do know a gun when it's pointed at them.
In the clip below, we learn that the train wreck that unleashes the monster "wasn't an accident" and in fact is a deliberate derailing by a scientist, Dr. Woodward. Is he a friend or foe? He seems friendly enough to warn our heroes that their lives are in danger. But then comes the gun.
There's also the fact he'd tried to take out an apocalyptic threat with only himself and a truck. Was he deliberately trying to free the thing?