'I shot him': Call made when inmate felled

The trial of the prison officer accused of murdering Dwayne Johnstone has heard his tiple-zero call. (PR HANDOUT IMAGE PHOTO) (AAP)

"I shot him," a prison officer known only as Officer A told triple-zero operators moments after he gunned down inmate Dwayne Johnstone in northern NSW.

The triple-zero phone call was played during a NSW Supreme Court murder trial on Thursday and was made by the officer, whose identity has been suppressed, on March 15, 2019.