The school confirmed all staff and students were accounted for.
An employee at the Challenge service station on SH56 said the road was cordoned off and their shop was closed.
A worker at the White Horse Inn said they could see "a lot of police cars" on the road and police all over a nearby property, "just checking everything out".
There were "dozens" of police on the property, he said.
The worker said police had been at the scene for a couple of hours.
He said police had earlier brought someone out of the property.
"I think they just surrendered themselves."
Police announced at 2pm the cordons had been lifted and the school had come out of lockdown.
They have arrested a 35-year-old man on a firearms-related offence.