National Guardsman missing after flash flooding devastates Ellicott City, Maryland: 'I'm hopeful that he'll be OK'

Maryland's governor declared a state of emergency in the wake of the flooding.

Rescue workers are searching for a National Guardsman who went missing after flash floods swept through Ellicott City, Maryland, on Sunday.

Hermond, a member of the Maryland National Guard, was at an Ellicott City restaurant with Joseph Lopez, his friend from the Air Force, when they noticed the parking lot starting to flood because of the heavy rain.

“It happened so fast," Lopez told ABC News. “The main street became a river in less than 20 minutes."

The friends were helping to block the restaurant doors to prevent flooding when one woman with a cat carrier wanted to leave, Lopez said.

Hermond was helping her when he lost his balance and was swept away into a river and under a bridge, Lopez said.

Hermond, who was wearing a white T-shirt and black shorts, hasn't been seen since, Lopez said.

“Eddison is a great swimmer so I'm hopeful that he will be OK," Lopez said.

First responders stressed this afternoon that the search to find Hermond is still a rescue mission, not a recovery mission.

His aunt, Deborah Nina Cooper, asked for privacy on behalf of the family but thanked well-wishers for their support.

"We are still working with government agencies as we remain hopeful that he will be found safe," Cooper said. "Please continue to keep Eddison in your prayers."

The governor of Maryland declared a state of emergency in the wake of the flash flooding in the historic mill town and other areas Sunday. Ellicott City saw 8.4 inches of rain in just a few hours. Nearby Catonsville, Maryland, saw over 10 inches of rain.

Howard County County Executive Allan Kittleman this morning called the flooding worse than the one that hit Ellicott City in 2016, killing two people and causing millions of dollars of damage.

“My heart's broken when I walk through the town and see it,” Kittleman told "Good Morning America." "All I'm thinking about is the folks whose lives have been devastated for a second time in two years."

“We are heartbroken to see the devastation that occurred yesterday," Maryland Gov. Larry Hogan said in a statement today. “State agencies have been working around the clock to coordinate resources, begin assessing damages, and clean up debris, mud, and damaged infrastructure.”

There were about 30 water rescues and 250 to 300 people were helped out of buildings amid the flash flooding, officials said.

Cheryl Nitz came to Ellicott City for a trip with her family Sunday when "it started raining ... and all of a sudden it just started raining harder and harder," she told ABC News. "Then we noticed the water was coming up over the curbs. Then all of a sudden the water was actually running down the middle of the street."

Nitz and her family raced up to higher ground to their car.

"We were able to get the car out of the parking spot and we moved toward Main Street," she said, but "there were other cars stuck in the way. We couldn't move."

The water rose so rapidly that her family had to be rescued from their car, she added.

"It rose so quickly probably within 5 or 10 minutes it just started to kind of cover the road... it was rushing," she said. "It was unbelievable."

Andrew Kolozsvary of New Hampshire was also visiting Ellicott City, enjoying a Sunday drive, when it started "raining pretty hard, so we decided to park the truck in front of the county welcome center," he told ABC News. "The water came and it came fast."

While in the truck, the quickly rising water was "inching the car along," he said.

After his rescue, the truck ended up washed down the street.

"I was glad to get out of it," he said. "The second deluge was the really bad one -- that took the truck."

Amber Twait was in Ellicott City as a band member for her friend's wedding Sunday when the venue flooded.

The couple ended up getting married at a nearby Mexican restaurant that was on higher ground, she told ABC News.

Eventually, Twait added, the restaurant started to flood as well, but not before they finished the ceremony.

"Obviously not ideal, but they were still able to say they're married at the end of the day," she said.

"It was a little scary, just because the lights were flickering but it was just really sweet and they both had such a good attitude about it," Twait added. "Hell or high water, they still were going to get married."

ABC News' Elizabeth McLaughlin, Fergal Gallagher and Sarah Shales contributed to this report.