He was very excited about the discovery of the small energy being creatures which inhabited the moon, unfortunately, the lifeforms turned violent and swarmed him, attacking him with vicious intent. Initially, their behavior had been peaceful and curious, but due to reasons unknown to the Stargate Command personnel, they turned hostile and lethally dangerous.
The beings turned against Thompson in a swarm-like fashion, stinging him and causing him great pain. Dr. Bill Lee who had accompanied Thompson managed to get back to the research facility to get for help. While Major Samantha Carter was tasked with keeping the scientists inside, Colonel Jack O'Neill and Teal'c raced to the clearing area where they found Thompson lying motionless on the ground. Unfortunately, it was too late as Thompson was already dead. (SG1: "Prodigy")