Why did Rodney King get beaten?

King and two other men in the car had been drinking heavily and driving erratically, after a high speed chase by the police, they managed to pull them over. The police stated that King was the most aggressive of the three and the force they used was justified, but it was caught on camera and the footage of this did not look justified. The four officers that beat him with batons caused broken bones and internal injuries. They were prosecuted for assault but were found not guilty, causing outrage and riots across America.