Dr Alan Billings said: “The killing of a police officer while on duty sends shock waves not only through the police service but through the wider community. It affects us all.
“It is a sober reminder to all of us that police officers, whose principal task is to keep us all safe, are constantly putting their own safety at some risk whenever they go on duty.
“In recent years we have seen a shocking rise in violence across the country towards all emergency service workers, not least the police. Our Violence Reduction Unit was set up last year to try to understand the extent of this violence in South Yorkshire and find ways of stopping people becoming involved in it in the first place, or to help them to turn their lives around if they are involved.
“In the meantime, our thoughts are with the family of the officer who has been killed in Croydon and in the light of that we should resolve to give the police here all the support we can as they seek to protect us in these difficult times.”