A 69-year-old man who suffered "multiple lacerations" and a 30-year-old woman was hurt, RCMP said.
Both victims were transported to hospital.
It all started when two people — one of which was the 30-year-old woman — were walking in the town, located on the shore of Hudson Bay, and encountered the bear at about 5 a.m.
They began shouting, and a 69-year-old man stepped out to investigate the commotion outside his home. That's when the bear turned on the man, RCMP said.
According to witness Doug Webber, who heard screams and looked out his window, the bear was on top of the man.
"All of a sudden we heard this screaming outside," said Webber. "[My daughter] said, 'There's a polar bear out here,' and I said, 'Yeah. OK, so?' and she said, 'There's somebody on the ground.'"
Webber said locals fired guns to try and scare the bear off but it wouldn't budge. So another resident tried something bigger.
"Another local resident was driving a vehicle and charged it toward the bear and scared the bear off," said RCMP spokeswoman Tara Seel.
After the attack, Webber helped get the man into another vehicle to take him to hospital.
“He didn't look OK. He was in a lot of pain and bleeding but his only concern was the girl,” Webber said, explaining the man had tried to distract the bear, which had attacked the woman.
"She looked pretty shaken and bloody. From what I understand she got bitten on the back of the head and around the ear."
Resident Joe Myles said on his Facebook site that he was outside having a cigarette break during his night shift at a hotel when a co-worker yelled about a bear sighting.
"I ran out to see a huge mama bear and her cub scurrying across the street from the back alley. Then we started hearing shots, then screaming and yelling, then more shots."
Myles said another bear came up the alley and "stopped and stared."
"We creeped back towards the door and had it half open just in case it came at us. Inside, the morning cook was frying bacon, which obviously interested the bear."
When the bear made a move towards them, they ran inside and shut the door.
Seel said officers from Manitoba Conservation tracked down the attacking bear and shot it.
"In the process of that tracking, another bear was shot and killed as well," she said.
It is not the first polar bear attack in Churchill this fall.
In September, a bear chased resident Garett Kolsun, trapped him on the porch of a bakery and swiped at him with his paw.
Kolsun pulled out his cellphone and the light startled the bear, which backed into a flower pot. That distracted the animal enough to give Kolsun a chance to run away.
Kolsun had only superficial puncture wounds and scratches.
The latest attack came just hours after trick-or-treaters would have been tucked in their beds.
Churchill takes special precautions on Halloween night. Several conservation officers circle the town in a helicopter to see if there are any bears around. Emergency vehicles are set up around the perimeter with their lights flashing to deter any curious creatures from checking out candy bags.
Churchill is near important polar bear summer habitat. The animals come through the area every year about this time when they move from the tundra back to seal-hunting territory — the pack ice that forms every winter over Hudson Bay.
John Iacozza is a senior instructor at the University of Manitoba. He studies polar bears and sea ice at the University of Manitoba and said right now, animals are waiting for Hudson Bay to freeze so they can go out and hunt.
“They’re going to be a little agitated, wanting to eat, and they may be a little more aggressive,” said Iacozza. “I think that’s what’s going on in Churchill.
In recent years, their return to their winter hunting ground has been delayed by the increasingly late formation of the sea ice caused by climate change.