He was found a short time ago hiding in a hallway at the school. No weapons were located on the individual.
The schools are no longer under lockdown.
Herald reporter Tristram Clayton said the scene had relaxed somewhat compared to the intense moments earlier when armed police rushed into the school.
A student spoke to Newstalk ZB's Leighton Smith from the chemistry lab at King's College while the school was in lockdown.
"The school told us just lock all the rooms, and go into the lockdown procedures that we have practised before," the student said.
"We heard helicopters circling the school. There was a SWAT team roaming the school as well.
"What we've been informed by the school is there is a dangerous person around the school and we need to remain in lockdown at the moment.
The 16-year-old student said a few people were worried but most people were doing their best to remain calm.
"The school's done well to handle the situation we've trained for the lockdown situation before, and we're following it as best as we can."
A student at one of the schools told the Herald by email: "My school went into lockdown about 9.30 and we haven't been allowed out of our classrooms since."
Another student emailed to say they were inside a classroom and had been told to keep quiet.
"We are in the classroom under the desks and we are safe at the moment. We are all messaging our friends and family."
He said there were 24 people sheltering in his classroom.
"We've have told nothing official from our maths teacher but my father who is at the golf course is also in lockdown."
The student said he and his classmates were told, "Go under our desks and do what we've practised in previous lockdown practices which is stay under our desks and be quiet".
A woman with two brothers attending King's College said they were seeking refuge.
"One is hidden in a room and the other is under his desk."
They had been told not to use their mobile devices, but had managed to get a short message through.
"One of them sent me a message to say they were safe.
"I am a bit scared for them, I don't want it to a copycat of what has happened in the United States."
A spokesman for the Royal Auckland Golf Club next door said police had asked them to get everybody off the golf course.
"We heard the King's College alarm go off, but police have given us no indication about what is happening, only saying to clear the golf course."