Michael Gerard van Delden (37) appeared in the Dunedin District Court this week after pleading guilty to two charges of threatening to kill.
His first rant took place on July 13 during a call to his Probation officer.
Van Delden was fuming about his dealings with Oranga Tamariki.
''I'm going to shoot you all, you c****,'' he said.
The officer said the defendant went into a ''full rage'' and she felt so intimidated she had ended the phone call.
When interviewed by police, van Delden clarified it was not the Probation officer with whom he was frustrated.
A month later he lost his cool again.
Van Delden was again speaking to the staff member and became agitated when Oranga Tamariki was mentioned.
He claimed he was going to get a machete and ''cut off their heads''.
''I'm coming back. You haven't seen the last of me. I'm coming back to get you,'' he added.
Van Delden said he was stockpiling food and was waiting for whoever was coming to get him.
When Oranga Tamariki was informed of the threats, it employed a security guard at its local offices for several days.
In a statement before the court, the Probation officer said she believed van Delden was capable of following through on his threats and she would be concerned if she saw him in public.
Defence counsel Deborah Henderson stressed there was no evidence her client owned either a firearm or machete.
She said he was in state care as a child, which went some way to explaining his ill-feeling for state departments.
''Whatever your resentment might be towards the Government and those employed by it, your conduct cannot be excused,'' Judge Michael Turner said.
''The people you threatened to kill were simply employees carrying out their statutory duties.''
Even if a home-detention address been available, the judge considered the offending too serious for van Delden to remain in the community.
Unlike other offenders, the man would not be subject to release conditions because he was trespassed from Corrections' Dunedin offices.
The court heard van Delden had previously spent time behind bars in 2017 for a similar threat against a civil servant.
