first responder
noun /ˌfɜːst rɪˈspɒndə(r)/
/ˌfɜːrst rɪˈspɑːndər/
(especially North American English)- a person such as a member of the police or fire department in a position to arrive first at an emergency, who has been trained to give basic medical treatment
- first responder training
- citizen/community first responders (= members of the public who have had special training for emergencies)