"If you want to be hard-nosed and callous about it - if he was travelling at the speed limit, he would still be alive, and so would the other gentleman," Gaskin said.
"It was obviously an incredibly high-impact crash. Two vehicles coming together at 100km/h in opposite directions produces an awful lot of kinetic energy - but one of the vehicles was travelling well in excess of that speed.
"One of the vehicles as a result of the impact has split and basically broken in half - half of that vehicle has ended up 40m to 50m up the road and across the fence and in a paddock," Gaskin said.
The driver of the northbound vehicle that split in half was thrown from his car.
The southbound car was taken to Timaru so firefighters could free the driver's body.
Police could not provide further details about the men until they were formally identified.
"Because of the injuries suffered it is going to take a little bit of time to do that," Gaskin said.
Glenavy Volunteer Fire Brigade chief fire officer Bevin Joyce said it rained overnight and was raining at the time of the crash.
He heard the northbound vehicle speed through town, and was not surprised to get the call to the crash, he said.
The initial report said a car was on fire, but that was not the case.
"The call was 'car on fire and rolled', but it hadn't actually ignited.
"There was a lot of heat generated and a lot of steam. There wasn't actually a fire," Joyce said.
The northbound vehicle had crossed the centre line, he said. The driver had been thrown from the car, which disintegrated on impact.
"This was totally preventable and it was just caused by speed and not driving to the conditions - and as a result there's two more fatalities," Mr Joyce said.
Traffic was rerouted along Glenavy-Tawai and Old Ferry Rds throughout the day.
The deaths took the holiday road toll to seven.
A few hours later, six people were injured when two cars collided near Orari, in South Canterbury.
Two of the six were taken to Christchurch Hospital with serious injuries. The other four were taken to Timaru Hospital with moderate injuries.
The crash happened at the intersection of Orari Station Rd and State Highway 1 about 11.30am.
In the Lindis Pass, one person was seriously injured and four people suffered minor injuries after a two-car crash near Omarama just before 5.15pm.
The patients were taken to Dunedin Hospital and Oamaru Hospital.
This year's holiday period started at 4pm on Friday and ends at 6am on January 4.
The other fatal crashes this holiday period were:
A female driver died in a three-car pile-up on SH5 near Hamurana in Rotorua on Sunday.
A person was killed Sunday in Pourerere Rd in central Hawke's Bay after a car rolled down a bank.
Boney Biju died on his way home from his 21st birthday party after his car left the road and hit a tree near Hanmer Springs on Christmas Eve.
Fijian national Lalita Devi was a passenger in a car that crashed on SH14 at Maungatapere on Saturday.
On Friday, taxi driver Abdul Raheem Fahad Syed, 29, died in central Auckland after his car was hit by another.
