William James Clark, 47, appeared in the Dunedin District Court yesterday where he pleaded guilty to a charge of threatening to kill.
Judge Deidre Orchard said the circumstances were "particularly serious".
On October 23, the Salvation Army staff member sent Clark a message informing him the organisation was unable to provide him with any new services.
Over the next four hours, the defendant unleashed his rage.
The 90 messages he sent were all "abusive and contained threats to kill the victim", court documents said.
"You are a dead b...., you lied to the wrong person, and I can’t wait to see you dead," one said.
"You are dead and mark the word dead because you are a f...... fraud."
Just hours later, a staff member saw Clark walking towards the Salvation Army premises.
"They activated their lockdown procedure, locking all the doors," a police summary said.
As Clark tried to enter the property, staff called police and he was arrested on site.
The defendant told officers he had made his comments "during the heat of the moment" and his lawyer couched it as a momentary lapse of control.
But Judge Orchard rejected that, pointing to the four-hour period over which the messages were sent and the attempt to gain entry to the business premises.
She said the victim, working in the role she did, was especially vulnerable.
Clark’s case was transferred to the Christchurch District Court where he will be sentenced in August.
