A shotgun and smoke bombs were reportedly used in the incidents, which took place at Runanga Workingmen's Club and the Railway Hotel.
Detective Senior Sergeant Kirsten Norton said that one person has been charged with aggravated robbery, attempted aggravated burglary, unlawful taking of a vehicle and commission of a crime with a firearm.
A second person has been charged with being a party to both an aggravated burglary and unlawfully taking a vehicle.
Witnesses to the Railway Hotel incident on Mawhera Quay called police when they saw a man standing outside the establishment with a shot gun.
The Greymouth Star understands the same man discharged two smoke canisters on the footpath outside.
Another witness said that they could see orange smoke billowing from the canisters from the Greymouth side of the Cobden bridge.
The canisters were left lying on the footpath alongside the pub.
Two armed police officers arrived at the Railway Hotel - one with a Bushmaster semi-automatic rifle.
The Police Big Day Out at the Grey District Aquatic Centre was interrupted as police were called to the incident.
“We know the community will agree that this sort of behaviour is absolutely unacceptable.
“We believe a third person may have been involved in these incidents and have knowledge that will assist Police.
“We also want to hear from anyone who may have dash cam footage, or saw anyone walking, between Cobden Bridge and Eight Mile Bluff north of Rapahoe on Friday 25 October between 10.50am and 1.30pm.
The firearm believed to have been used during the aggravated robbery has been recovered.
The two men are due to appear in at Greymouth District Court on Tuesday 29 October.
If you have information that may assist Police, please call 105 or Crimestoppers anonymously on 0800 555 111.
- Additional reporting Greymouth Star
