Taken and paraphrased from the "Officer Down" Memorial Page:

Officer Ryan Bonaminio was shot and killed while involved in a foot pursuite in Fairmont Park.

He had stopped the driver of a tractor suspected of being involved in a hit-and-run accident a short time earlier.  The driver fled from the vehicle into the park, with Officer Bonaminio in pursuit.

As Officer Bonaminio rounded a corner of a church he slipped and fell, at which point the suspect struck him on the head with a metal pipe and disarmed him.  The suspect then shot Officer Bonaminio in the head twice despite the officer's pleas not to shoot.  Officer Bonaminio was transported to a local hospital where he succumbed to his wounds a short time later.

Suspect was Sentenced to death.

Officer Bonaminio had served as a military policeman in the U.S. Army for four years, serving two tours in support of Operation Iraqi Freedom.  He also served with the Riverside Police Department for four years.

Ryan Bonaminio was 28 years of age.