Musician Billy Ray Cyrus sang a song he wrote for soldiers of the Vietnam War at a service for a 22-year-old police officer killed in the line of duty.

He said that Davis Officer Natalie Corona’s smile touched his heart.

He called her a “light in this world that won’t be forgotten”.

Bagpipes played as pallbearers solemnly carried her flag-draped coffin to a packed memorial at the University of California, Davis.

All 8,000 seats are filled with officers, family, friends and members of the community to bid farewell to Ms Corona.

Davis Police Chief Darren Pytel posthumously awarded the Purple Heart and a medal of distinction at a packed memorial service for Natalie Corona.

Officer Killed California Funeral
Musician Billy Ray Cyrus performs a song (Rich Pedroncelli/AP)

Ms Corona was shot and killed last week when she responded to a three-car crash.

Police are still investigating the motive for the attack.

The gunman has been identified as a 48-year-old convict who was banned from owning firearms and took his own life after shooting Ms Corona.

Mr Pytel says that although the person who “committed this atrocity” is known, why he did it may never be.