He would give her and her sisters pocket money for doing odd jobs around the house.
Mr Morrissey said there was no doubt that his money was the "number one" thing the youths were after.
"That's what the operation was," he said.
The teens then barged past Mr Morrissey, knocking him to the ground.
As he fell he hit a coffee table, cutting his arm and knee.
The youths repeatedly asked where his money and wallet were.
Mr Morrissey offered the pair $100 if they left him alone, but eventually they found his wallet and took about $400.
Mr Morrissey wears a St John medical alarm and activated it as he lay on his lounge floor.
"I was frightened they would hit me on the head. It was all a sort of blurry panic," he said.
His son, who lives nearby, was able to get to Mr Morrissey shortly after the teens fled after being contacted by St John.
Mr Morrissey, who has poor eyesight, said he could not clearly see the pair but said one was wearing a white shoe and a black shoe. APNZ