In a statement this evening police said they were called to a Park Street address around 1pm after reports a firearm had been discharged.
They arrived to find a man with gunshot wounds, who was taken to Southland Hospital, where he was reported to be in a serious but stable condition.
Police and armed offenders squad members attended, cordons were put in place and nearby schools were put into lockdown as a precaution, police said.
A 19-year-old man was later located in Invercargill and arrested. There was no word on any charges he would be facing
Earlier this evening St John said one person had been taken to hospital in a critical condition.
This afternoon, an Otago Daily Times reporter on her way to the scene said she pulled over to make way for three ambulances heading towards Invercargill.
The lockdown affected Winton School, which said on Facebook this afternoon police had advised it was now safe to come out of lockdown.
"As per normal, children will be released from their classrooms at 2.45pm."
It had earlier said the school had been in lockdown since 1.15pm after a police directive.
"After many drills over the past few years, all students and staff have responded quickly and are safe in their allocated spaces."
Streets around the scene were cordoned off including Park St, Brandon St and Arthur St, with traffic being diverted by police.
Reporter Toni McDonald said armed police were at the scene.
Also affected was Winton Kindergarten, but children were allowed to leave about 2.30pm through a side gate where parents waited to take them home.
A Central Southland College spokeswoman earlier said the school was in lockdown and a message had been sent to parents via the schools app.
''We've done everything we can, we're just waiting to hear [from police].''
A St John spokeswoman confirmed they were called to the scene at 1.21pm.
