Mr Mathieson, who has run the complex for 17 years, suffered a broken shoulder blade, three broken ribs, fractured vertebrae and a broken hip joint and is expected to remain in North Shore Hospital until the weekend.
His wife Lou and their three adult daughters are now asking the public to turn the teen in to police.
"We just want to make sure it won't happen to somebody else," said Mrs Mathieson.
"You can't just go on to someone else's property and think that's okay and then assault somebody.
"If they catch him it means he won't be able to do it again."
Police flooded the area on Hurstmere Rd soon after the incident, which happened at 9.20am.
The teenager is yet to be found.
However, a police spokeswoman said there had been an influx of information from the community.
"Police are following strong lines of enquiry in relation to the incident," she said.
"A number of calls have been received from members of the public and we thank the Takapuna community for their help."
Mrs Mathieson is still shaken by the ordeal, and has taken on her husband's workload while he recovers.
He was in "awful lots of pain," she said.
"He's got some serious drugs going on, he actually can't move. I don't know what's going to happen when he has to."
Mrs Mathieson was still in the couple's on-site apartment when police called her about 10am.
She said her husband had managed to reach his phone and call police himself.
"I went to where he was, down the bottom of the stairs. He couldn't move. We had to wait for an ambulance from there.
"He couldn't talk very well, but I was trying to find out what had happened and so he was telling me ... and asking me where the ambulance was because he couldn't stand up; it was really painful for him.
"He's manager of the complex and this guy was inside ... and there's 138 apartments so I imagine he was thinking he was protecting everybody in there. He didn't want this guy running loose."
The offender has been described as a Maori in his late teens, of stocky build and wearing a black singlet, black jeans and with a white and blue T-shirt around his face.
Anyone with information is asked to contact Sergeant Todd Bartlett on (09) 477 5261.