A husband watched in horror as an oncoming car smashed head-on into his wife's vehicle, travelling behind his.
Both the oncoming motorist, 54, and the woman, 51, died at the scene of the crash.
The husband, towing a caravan, and wife, from Puhoi, had been travelling north when the crash happened at the intersection of State Highway 1 and Richards Rd at Hikurangi, Northland, just after 2pm yesterday.
Police said the southbound Mazda had ripped the side off the caravan before ploughing straight into the following car.
"The tragedy is, the woman who was killed was the wife of the man towing the caravan," Sergeant Chris Goodall, from the Whangarei highway patrol, said.
"The husband wasn't physically injured but was obviously in a state of complete shock. It is a terrible waste of life."
Richards Rd resident Viv Croft was one of the first people at the scene. "I heard a big bang and ran out the house to see what was going on," she said. "The whole thing was a bloody mess and it was clear the two people were already dead in their cars, and the caravan was pretty munted.
"There was nothing anyone could do for the people. It was clear they were already gone."
Croft said she helped direct traffic while another passer-by phoned 111.
"I don't understand how it could have happened because it was on a straight stretch of road."
Police serious crash unit and other emergency services rushed to the scene and traffic diversions were put in place for the rest of the afternoon.
"Driving conditions were good and our focus is on why the driver of the Mazda crossed the central line," Goodall added. "It was a very grim scene indeed.
Snow Buckton, fire chief at Hikurangi, was at the crash site within minutes. He said the bodies of both the deceased had to be cut from their vehicles.
"It used to be a bad accident spot until the layout of the road was changed a few years ago. I had not attended a crash there for a long time," Buckton said.
"We had three fire trucks and a support van in attendance and there was a lot of police and ambulance there too. It was a very sad scene and not a pretty site."
Goodall said next of kin had been informed but the victims were not likely to be named until later today.