Wiktionary
first responders
n. (first responder English)
Wikipedia
First Responders (The Unit)
"First Responders" is the pilot episode of the American drama series The Unit, created by David Mamet. It originally aired on CBS on March 7, 2006.
Usage examples of "first responders".
The Arab guards and Israeli first responders were putting up a far tougher fight than they'd expected.
If the agent was contagious in human-to-human transmission, then just about the first people to die would be the medical caregivers and the first responders.
He mentioned big budget increases for the FBI, CIA, firefighters and others, the first responders to terrorist attacks.