The aliens are more or less humanoid.
I think they’re not outright hostile at first but something goes wrong during their first contact with humans, which leads to both sides becoming aggressive and the aliens are being hunted from then on.
The aliens set up makeshift traps in the woods but eventually all of them are killed by the locals. A medical doctor examines their bodies and by observing their skull sutures, he determines that they were practically kids. That’s the punchline of the movie, when the characters realize that what they saw as monsters were actually a group of adolescents, who panicked in a foreign environment encountering a species (the humans) they’ve never met before.

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