In the beginning the particle accelerator exploded from S.T.A.R labs. It was made by doctor Harrison Wells he is a scientist or owner of S.T.A.R labs in earth two

The particle accelerator made lots of meta-humans including bad ones mostly bad ones. One meta-human was a speedster he was very fast,fast as lightning.

He was called Zoom who used to be a murderer called Hunter  Zolomen. He killed thirty-two peoples.

After, he turned into a villain.