A New Mexico firefighter, Matthew Sanchez, has resigned from the city's dispatch centre after telling a 911 caller who was trying to keep alive a gunshot victim to "deal with it yourself."

"An internal investigation has been initiated," Albuquerque Fire Chief David Downey said Monday in a statement. "I am taking the allegation very seriously."

The call was made after Jaydon Chavez-Silver, 17, was shot in June as he watched other teens play cards at a friend's house in Albuquerque. He later died. Police have not named a suspect and have made no arrests.

'I am keeping him alive!'

In the recording obtained Tuesday by The Associated Press, the panicked caller snaps at the dispatcher for repeatedly asking whether Chavez-Silver is breathing.

During the call, the female says, "I am keeping him alive!"

Sanchez asks, "Is he not breathing?"

The caller responds, "Barely!"

She is then heard frantically encouraging Chavez-Silver to keep breathing.

"One more breath! One more breath!" she is heard telling the teen. "There you go Jaydon. One more breath! There you go Jaydon. Good job! Just stay with me, OK? OK?"

The dispatcher then asks again, "Is he breathing?"

The female responded, "He is barely breathing, how many times do I have to (expletive) tell you?"

"OK, you know what ma'am? You can deal with it yourself. I am not going to deal with this, OK?" the dispatcher says.

It seemed from the tape that Sanchez hung up on the caller in mid-sentence.

"No, my friend is dying ..," she said as the call ended.

A spokesman for Jaydon's family said they're astonished at the call, but want to focus on finding their son's killer.