Torrential rain sent water rushing into Ellicott City on Sunday for the second time in less than two years.
Governor Larry Hogan toured the area and promised "every bit of assistance we possibly can".
Kittleman said the damage was significant and appeared to him to be worse than the flooding two years ago. On Sunday, the community received almost 8 inches (20.32 centimetres) of rain over a six-hour period, but most of it fell during an intense, three-hour period, Muccilli said.
Muccilli said Sunday's rain created "a true flash flood". Flash flooding and water rescues are being reported in Maryland as heavy rain soaks much of the state.
In one instance, a wedding party was forced to flee the Main Street Ballroom when the waters burst through the doors.
"They say this is a once every 1,000-year flood and we've had two of them in two years", Hogan said.
A friend of Hermond's told WTOP that the veteran had been in a restaurant in downtown Ellicott City on Sunday; witnesses said he was swept away after trying to help people.
Officials said 30 rescues were carried out into Monday morning, whereby the half-foot of water had receded and residents could survey the damage to their homes and businesses. There were not immediately any reports of injuries or fatalities.
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The newspaper reports that the swirling waters reached the second flood of one building at its height.
Just two weeks ago, the Federal Emergency Management Agency gave the county $1 million to fix a culvert and replace a runoff pipe with a larger one.
An SOS flag hangs from a building during the flooding on Main Street of Ellicott City, Maryland.
"If you don't have to be outside, you shouldn't be", Baltimore County Fire Department spokeswoman Elise Armacost said in a statement obtained by The Sun. However, two people died in similar flooding in July 2016.
Some Baltimore County roads were also flooded.
A flash flood emergency was issued in Maryland's Howard County at 4:40 p.m.
Ellicott City is an unincorporated community about 12 miles west of Baltimore.
Officials are urging anyone in the area to seek higher ground and not to drive through flooded roads.