Two women suffered serious injuries after they were shot at a Rolleston property.
The arrested man is known to both his victims, who are in Christchurch Hospital being treated for gunshot wounds.
Then, about 11.20pm, an armed robber entered the Ashburton Hotel on Racecourse Rd, firing a shot into air before taking cash.
Detective Inspector Darryl Sweeney said up to five people were inside the hotel at the time. Nobody was injured when the gun was fired inside the bar. The man is also a suspect in the hotel robbery.
Neighbours to the shooting at the house were shocked this morning.
A neighbour, who doesn't want to be named, says the injured women are a mother and daughter and describes them as lovely people, the first to offer help when you need it.
Inspector Corrie Parnell said specialists would be examining a number of properties across the region today as the investigation continued.
A large cordon surrounded Newtons Rd about 9.30pm and dozens of police and ambulances descended on the area after neighbours heard gunfire.
The cordons were no longer in place but the property was under guard while detectives pieced together what happened.
The hotel was closed overnight and Ashburton Police will examine the scene today.