More than 100 officers from various agencies are battling with the snowy conditions as they continue the search for a former Los Angeles police officer accused of killing three people because he felt he was unfairly dismissed from his job.
More top news
The memorial service will be attended by Prince Harry and Meghan Markle.
David Browning admits manslaughter by diminished responsibility but denies murder.
Four people have died and the suspect is still at large, police said.