WILMINGTON, N.C. – Hurricane Florence splintered buildings, trapped hundreds of people and swamped entire communities along the Carolina coast Friday in what could be just the opening act in a watery, two-part, slow-motion disaster.

At least five people -- including a mother and her baby killed when a tree fell on a house in Wilmington -- were killed. Police officers believe the baby was about 8 months old, and they said the baby's father was seriously injured and remained hospitalized. Firefighters kneeled down to pray after finding them dead. 

A 78-year-old man was electrocuted when he attempted to connect extension cords out in the rain in the city of Kinston, according to Lenoir County authorities. The wind pushed a 77-year-old man who was checking on dogs in Lenoir County. 

A woman died of a heart attack when downed trees prevented paramedics from getting to her on time in Hampstead, North Carolina, according to Pender County authorities, ABC News affiliate WWAY-3 reported. 

11 PM REPORT | Local 10 News reporter Andrew Perez reports from North Carolina

11 PM ADVISORY | Local 10 News Weather Authority

The storm surge, the ocean water pushed over the land by the onshore winds, will peak on Saturday. It could take weeks for the flooding to subside. Life-threatening flash floods over portions of the Carolinas and the southern to central Appalachians will continue through early next week.

As 400-mile-wide Florence pounded away at the coast with torrential downpours and surging seas, rescue crews used boats to reach more than 360 people besieged by rising waters in New Bern, while many of their neighbors awaited help. More than 60 people had to be rescued in another town as a cinderblock motel collapsed at the height of the storm’s fury.

PHOTOS | Rescue workers in North Carolina

Florence flattened trees, crumbled roads and knocked out power to more than three-quarters of a million homes and businesses, and the assault was not anywhere close to being over, with the siege in the Carolinas expected to last all weekend.

"It’s an uninvited brute who does not want to leave," said North Carolina Gov. Roy Cooper.

The hurricane was "wreaking havoc" and could wipe out entire communities as it makes its "violent grind across our state for days," the governor said. He said parts of North Carolina had seen storm surges — the bulge of seawater pushed ashore by the hurricane — as high as 10 feet.

A mother and baby were killed when a tree fell on a house, according to a tweet from Wilmington police. Also, a 77-year-old man was apparently knocked down by the wind and died after going out to check on his hunting dogs, Lenoir County authorities said, and the governor’s office said a man was electrocuted while trying to connect extension cords in the rain.

LIVE UPDATES | Map by United States Geological Survey tracks flood events

Shaken after seeing waves crashing on the Neuse River just outside his house in New Bern, restaurant owner and hurricane veteran Tom Ballance wished he had evacuated.

"I feel like the dumbest human being who ever walked the face of the earth," he said.

After reaching a terrifying Category 4 peak of 140 mph earlier in the week, Florence made landfall as a Category 1 hurricane at 7:15 a.m. at Wrightsville Beach, a few miles east of Wilmington and not far from the South Carolina line. It came ashore along a mostly boarded-up, emptied-out stretch of coastline.

By Friday evening, Florence was downgraded to a tropical storm, its winds weakening to 70 mph as it pushed inland. But it was clear that this was really about the water, not the wind.

Florence’s forward movement during the day slowed to a near-standstill — sometimes it was going no faster than a human can walk — and that enabled it to pile on the rain. The town of Oriental, North Carolina, got more than 20 inches just a few hours into the deluge. Other communities got well over a foot.

PHOTOS | Flooding in North Carolina began Thursday

The flooding soon spread into South Carolina, swamping places like North Myrtle Beach, in a resort area known for its white sands and multitude of golf courses.

For people living inland in the Carolinas, the moment of maximum peril from flash flooding could arrive days later, because it takes time for rainwater to drain into rivers and for those streams to crest.

Preparing for the worst, about 9,700 National Guard troops and civilians were deployed with high-water vehicles, helicopters and boats.

Authorities warned, too, of the threat of mudslides and the risk of an environmental disaster from floodwaters washing over industrial waste sites and hog farms.

Florence was seen as a major test for the Federal Emergency Management Agency, which was heavily criticized as slow and unprepared last year for Hurricane Maria in Puerto Rico, where the death toll was put at nearly 3,000.

PHOTOS | Satellite images of Florence

The National Hurricane Center said Florence will eventually break up over the southern Appalachians and make a right hook to the northeast, its rainy remnants moving into the mid-Atlantic states and New England by the middle of next week.

Florence is likely to dump rain over a week on North Carolina, South Carolinas, Virginia, Georgia, Tennessee, Kentucky and Maryland. That’s enough to fill the Chesapeake Bay or cover the entire state of Texas with nearly 4 inches of water, he calculated.

North Carolina alone is forecast to get 9.6 trillion gallons, enough to cover the Tar Heel state to a depth of about 10 inches.

On Friday, coastal streets in the Carolinas flowed with frothy ocean water, and pieces of torn-apart buildings flew through the air. The few cars out on a main street in Wilmington had to swerve to avoid fallen trees, metal debris and power lines.

A wind gust at the Wilmington airport was clocked at 105 mph (169 kph), the highest since Hurricane Helene in 1958. Nationwide, airlines canceled more than 2,400 flights through Sunday.

In Jacksonville, North Carolina, next to Camp Lejeune, firefighters and police fought wind and rain as they went door-to-door to pull dozens of people out of the Triangle Motor Inn after the structure began to crumble and the roof started to collapse.

In New Bern, population 29,000, flooding on the Neuse River left 500 people in peril.

“WE ARE COMING TO GET YOU,” the city tweeted around 2 a.m. “You may need to move up to the second story, or to your attic, but WE ARE COMING TO GET YOU.”

Boat teams including volunteers rescued some 360 residents, including Sadie Marie Holt, 67, who first tried to row out of her neighborhood during Florence’s assault.

“The wind was so hard, the waters were so hard, that trying to get out we got thrown into trailers. We got thrown into mailboxes, houses, trees,” said Holt, who had stayed at home because of a doctor’s appointment that was later canceled. She retreated and was eventually rescued by a boat crew; 140 more awaited assistance.

PHOTOS | Dangerous fallen trees

Ashley Warren and boyfriend Chris Smith managed to paddle away from their home in a boat with their two dogs, and the experience left her shaken.

“Honestly, I grew up in Wilmington. I love hurricanes. But this one has been an experience for me,” she said. “We might leave.”

Hurricane Survival Guide

Associated Press writer Jonathan Drew worked on this story. Associated Press writers Seth Borenstein in Washington; Allen G. Breed in New Bern, North Carolina; Jeffrey Collins in Myrtle Beach, South Carolina; Jennifer Kay in Miami; Tamara Lush in Jacksonville, Florida; Gary Robertson in Raleigh, North Carolina; Sarah Rankin and Denise Lavoie in Richmond, Virginia; Meg Kinnard in Columbia, South Carolina; Skip Foreman in Charlotte, North Carolina; Jeff Martin in Hampton, Georgia; David Koenig in Dallas; Gerry Broome at Nags Head, North Carolina; and Jay Reeves in Atlanta contributed to this report.

ABC News' Daniel Manzo and Emily Shapiro also contributed to this report.