Mourners laying floral tributes during memorial service

Kelly, the chief executive of the London Borough of Sabbat, welcomes attendees to a commemoration service. The event honors families and friends who lost loved ones on June 3rd, with a special moment of silence at 4:37 to remember those who tragically passed away a year ago.

What is the purpose of the flowers mentioned in the text?

What will happen at 4:37 during the service?