A 15-year-old "gentle giant" who allegedly stabbed a man who was burgling his West Auckland home had been the victim of a break-in a few months before.

Police said a 19-year-old man was admitted to Auckland Hospital with stab wounds to his torso yesterday after he entered the property in Alan Ave, Henderson, and was disturbed by a man and his 15-year-old son about 1am.

Detective Senior Sergeant Stan Brown said police understood the father and his son woke to noises on their property.

"They went to investigate and located an intruder in their garage. A scuffle ensued, during which time the 15-year-old son stabbed the intruder.

"Police were promptly called and the intruder was taken to Auckland Hospital.

"His injuries are not considered to be life-threatening," Mr Brown said.

A neighbour said the teenager had had his trail bike stolen from the garage several months ago.

Patricia Edmonds said that, from talking to the family, they believed the burglar was the same person who had burgled them previously and was returning to steal the new bike that had been bought with insurance.

"He was obviously targeting something in the garage. They've heard the racket going on and gone: `Oh, no'."

Mrs Edmonds said the burglar was trying to "saw" through bars that had been put over the garage windows.

"If he [the boy] has done anything, it was spur of the moment. He's not at all violent. He would have been just trying to protect his dad."

She said the teenager was lovely.

"He's a very quiet boy. He's not a partygoer. He's a big kid but he's a gentle giant. He's not a tiny skinny boy."

The boy goes to a local high school, where he is involved in a band.

"I think he'd be horrified, if anything," Mrs Edmonds said.

The boy's father looked upset when approached yesterday and declined to comment.

Police said a "thorough investigation" was under way. They had not decided last night whether any charges would be laid.

Auckland pharmacist Grant Gillard, who restrained a burglar who died in his store last year, said it would be a "tough thing" for the family to go through.

"You just go into a situation, you haven't done anything to cause this. You realise it's him or you because they are fairly desperate people. You use any force you can to make sure you come out all right, otherwise you'd be the one lying dead on the floor."

Mr Gillard said he did not think the boy should be charged, though, "in reality, it goes through due process".

He said he had faith in the police process after the decision not to charge him but it did "drag on". "It can be worrying."