Officials hadn't immediately confirmed the man's name.
About 162,000 homes and business customers were already without power around mid-afternoon in Florida, Georgia and Alabama, utility companies said. By 8pm, it was down to a category 1.
The storm made landfall near Mexico Beach, Florida, at around 2 p.m. ET.
"We haven't seen her since the tree hit the den". Cloud water releases a burst of heat, and hurricanes love heat.
He has covered hurricanes in the state for decades.
"I'm anxious about my daughter and grandbaby". "It's like a nightmare". You are not going to survive it. How can this happen?
"Going back through records to 1851 we can't find another Cat 4 in this area, so this is unfortunately a historical and incredibly unsafe and life-threatening situation", he said.
Numerous buildings in Panama City were demolished, partially collapsed or without roofs amid deserted streets littered with debris, twisted, fallen tree trunks and dangling wires.
The National Hurricane Center says Hurricane Leslie and Tropical Storm Nadine are no threat to land over the open Atlantic Ocean, but Tropical Storm Sergio is expected to hit Mexico's Baja California Peninsula later this week and threaten the southern U.S. Plains and the Ozarks by the weekend.
It will take some time for residents of north Florida to take stock of the enormity of the disaster.
An AccuWeather meteorologist captured Hurricane Michael's intense eye wall on the east side of Panama City Beach.
More than 40 percent of daily crude oil production and more than one-third of natural gas output was lost from offshore US Gulf of Mexico wells on Wednesday because of platform evacuations and shut-ins caused by Michael.
An estimated 6,000 evacuees took cover in emergency shelters, majority in Florida, and that number was expected to swell to 20,000 across five states by week's end, Mr Kieserman said. However, even at a lower category, the storm will pose a major threat.
"I'll be traveling to Florida very, very shortly and I just want to wish them all the best".
People in coastal parts of 20 Florida counties had been told to head to safer locations, but by Wednesday morning were told it was too late to flee. "We will take care of each other".
"Storm surge estimates are anywhere between nine and 14 feet". Coupled with that you have over 145 miles per hour winds. The roar from the hurricane sounded like an airplane taking off.
Where is Hurricane Michael NOW?
"I guess it's the worst-case scenario".
"The timing was ghoulishly flawless", said Weather Underground meteorologist Bob Henson. "This is going to have structure-damaging winds along the coast and hurricane force winds inland".
"We are in new territory", National Hurricane Center Meteorologist Dennis Feltgen wrote on Facebook.
"The historical record, going back to 1851, finds no category four hurricane ever hitting the Florida panhandle". Palm trees whipped wildly in the winds.
Trump issued an emergency declaration for Florida, freeing up federal funds for relief operations and providing the assistance of FEMA, which has more than 3,000 people on the ground.
Briefing Mr Trump, Brock Long, the United States government's disaster chief, said: "This is the most intense hurricane that's struck this area since 1851". He acknowledged that a lot of the residents in the area were poor and said it was probably tough to leave.
Hurricane Michael knocked down hundreds of trees on Wednesday in Tallahassee, Florida. Amtrak has also modified its service and is waiving fees for passengers who change their reservations.
After there, the storm will move up through the Carolinas, hit by heavy rains form Hurricane Florence just a few weeks ago.
Heavy rainfall was projected for areas in the storm's path.
By Tuesday, Michael had reached Category 2 strength.