Department of Conservation ranger Rod Hansen said the dolphins sought refuge in the shallow waters of the beach and Te Angiangi Marine Reserve reef.
The pod continued north to Aramoana Beach but soon word spread the dolphins had returned.
Mr Petersen's 16-year-old grandson Hamish Hewitt paddled out to the dolphins, along with neighbour Frank Lochore, on their surfboards.
"They shot off and then these two big fins came along," Hamish said.
"We looked at them a bit and Frank said, 'I don't want to be the first one eaten by an orca,' so we quickly caught a wave in."
Mr Petersen was watching the action from his verandah.
"We were elated and my son-in-law with a pair of binoculars said, 'Hey there's a couple of dolphins stranded on the reef'."
Mr Hansen said locals quickly saved the mother and 1m calf caught out by the outgoing tide, directly opposite Wazmacs Camp.
"It was really good. All the locals just got together, rolled up their sleeves and got into it."
Using beach towels as a sling, the dolphins were moved from the shallow water to the sea, with the calf moved first.
The mother called to it constantly, keeping it close to the reef, Mr Hansen said.
"They swam around for a while. We are not sure if they were confused or didn't want to go back into the deep.
"The mother was bleeding slightly from damage on the reef - I don't think it was anything that was going to harm her."
The dolphins slowly moved out to sea.
Mr Petersen said the pod returned to Blackhead Beach because of the cries of the stranded dolphins.
"They came right into the bay, right into the breakers and up to the reef.
"Once we found the ones stranded we were pretty sure they had come back answering the distress call."
Floppy Halliday, founder of Northland's Whale Rescue, said there was no record of New Zealand-based orca eating dolphins, but visiting orca had.
She asked if anyone had recent photos of orca in Hawke's Bay to send them to floppysdolphins@hotmail.com, to help identify their origin.