Within 12 hours of the fatal earthquake, Mr Stock was at home in Wanaka.
He was uninjured but still shaking from the traumatic experience of witnessing casualties and destruction.
Mr Stock never went back to his Crown Plaza Hotel room to collect his possessions.
Instead, he left the city in a borrowed car, taking nothing but what he had in his pockets.
"I must admit when I got home I was still shaking and I felt things were still rocking," Mr Stock said.
"I did what I could to assist, then I got out of the way... It was not until afterwards you realise how close to death you have been."
Mr Stock is the general manager of Edgewater Resort and was in Christchurch on Tuesday for a board meeting with his Christchurch directors.
He was having lunch with chairman Mike Souter at the MegaWatt kitchen at 218 Manchester St when the quake struck.
"There was just a massive crunch and I thought something had hit the building. Straight behind it was another one. At that stage, something just kicked in for me, and I just went," he said.
Mr Stock believes he was first out the door.
He ran into the middle of Manchester St.
As the ground rolled under him, he saw facades falling from buildings.
"Directly opposite where I was, a facade just fell and crushed this car. I saw a gentleman sitting in the car and it was just crushed to this high," Mr Stock said, indicating to his knees.
He has learned the man was later extracted but says the man could not have survived.
"There was nothing I could do."
As car alarms and sirens blared, he found Mr Souter crouching near the cafe.
"I had left my mobile phone on the table so I thought I would open the door. From the outside, the building looked relatively unscathed. It was just a war zone in there. The ceiling had collapsed internally and a big ceiling fan was on the table where we had been sitting," he said.
He moved ceiling panels to find his jacket and phone, then rang home to report he was safe.
The phone system then crashed.
As he crossed a bridge over the Avon River to a safer place, he noticed the small, bluey-green stream was rising and changing to a milky brown colour.
The Pyne Gould Corporation building came down but in his shock, he didn't hear or see it happen.
"The dust and clouds reminded me of what you saw from 9/11. There was no movement of the Pyne Gould building. It just went woomph. It was surreal. I didn't see it and asked, 'When did that come down?'"Then we saw a woman standing on the roof and we pointed her out to the fire brigades and she was rescued," Mr Stock said.
The men walked to Merrivale, where the smell of gas was everywhere and aftershocks kept coming.
They were driving away in a borrowed car when the second earthquake struck, just before 3pm.
Poles moved, the road rose up before them and liquefaction emerged.
By 4.30pm, Mr Stock was driving out of the gridlocked city, one of many escapees heading south.
