Instead, the teenager headed back to his bedroom and phoned the police.
Mr Lacey said he tried to defuse the situation, but the intruder was oblivious to anything he was saying.
"Eventually, I managed to get free of him. I ran outside, got into my car and drove to the neighbour's house, where I believed my boy was."
He returned home with a friend to find the police waiting for him and the two boys barricaded in the front room, but the intruder had decamped.
"Afterwards, the boys told me how they heard the man stomping up and down the hallway."
Mr Lacey said he had no idea who he was: "It was just a random attack, I believe."
"In all the 40-odd years I have lived in Runanga nothing like this has every happened before. We are still in shock. It was like something you see on the tv news, not Runanga."
His son was too frightened to stay home, spending the night at his grandparents' house.
Acting Senior Sergeant Brent Cook, of Greymouth police, said they had a good description of the suspect and were following "good lines of inquiry".
"We would also appreciate any information from people in the Runanga area who may have seen suspicious activity at the time of the incident."
Mr Lacey said the offender was aged in his late 20s or early 30s.
