Neither Higgins nor state police would say which of the victims was the pilot.
Two of those aboard the helicopter were members of the Frederick County Chamber of Commerce.
A Chamber spokesperson said Felix was a regional sales manager for Tele-Plus Corp, which sells communications systems, and that Booth was director of Heli-Flights for Hope and CEO of SalesBridge Solutions, a consulting business.
The bodies were taken to the state medical examiner in Baltimore, said Kevin Lewis, director of Washington County Emergency Services.
No one on the ground was injured in the crash of the Robinson R44 helicopter east of Hagerstown on South Mountain, authorities said.
The helicopter gave rides to benefit a charity following a Thursday night meeting of the Fort Detrick Alliance at the Hagerstown Regional Airport, Higgins said.
The flights to benefit the Advanced Helicopter Youth Foundation took place between 4 and 8 p.m. Thursday, Higgins said.
After the final flight, the pilot waited for two hours before starting his return trip to Frederick, Higgins said.
The pilot took off at 10:15 p.m., Higgins said. It was a visual flight, with no contact with air traffic control and no flight plan, she said.
The pilot was not required to file a flight plan, Higgins said.
She said it was not known if the aircraft had instruments that would allow him to fly in bad weather.
The pilot's medical certification had recently been updated, Higgins said. He had 630 hours of experience and was certified as a commercial pilot for both helicopters and fixed-wing aircraft, she said.
Witnesses saw the helicopter flying low, Higgins said. The copter struck power lines about 70 feet above the ground, she said.
Higgins said the helicopter was destroyed on impact. The cabin was consumed by fire and was not survivable, she said.
Higgins said it is not known how familiar the pilot was with the area. She said a witness described the weather at the time of the crash as clear close to the ground, but foggy higher up.
Higgins said it is believed all of the wreckage has been recovered. It is being kept at a hangar at Hagerstown Regional Airport and will be taken to Delaware for further inspection, she said.
NTSB officials arrived at the scene at about 12:30 a.m. Friday, Higgins said.
She said investigators would examine the helicopter's maintenance records and the pilot records. They will interview witnesses and first responders, and examine the weather conditions at the time of the crash.
There was fog in the area where the crash occurred and visibility was limited, Lewis said Friday.
Maryland state police said a trooper who was driving east on I-70 came upon the scene just after the crash, which was reported at about 10:30 p.m.
High-tension wires were down at the scene, blocking both eastbound and westbound lanes of I-70, Lewis said. The interstate in the area was closed until around 5 a.m. Friday.
Firefighting units from Mount Aetna and Myersville, Md., were the first to arrive and extinguished the fire in about 20 minutes.
Community Rescue Service, Inc. and units from Funkstown also responded to the crash site and Hagerstown Regional Airport officials were called in, Lewis said. Hagerstown Regional Airport manager Carolyn Motz was at the scene.
Maryland State Police and National Transportation Safety Board officials were handling the investigation.
Advanced Helicopter Concepts began operations in 1987 at the Frederick Municipal Airport in Frederick, according to the company's Web site.
"Our main focus is providing helicopter training. We also offer aerial platforms for photographers and videographers," the Web site says.
The company also specializes in aircraft maintenance, powerline and pipeline patrol and provides helicopter introductory rides and lessons, according to the Web site.
Chris Dancy, spokesman for the Aircraft Owners and Pilots Association, which is based at the Frederick airport, said the crash "caught a lot of people by surprise."
He described the R-44 four-passenger helicopter as "generally a very reliable helicopter" that is "more commonly used for training."
Sandy Geer, chief flight instructor at Frederick Flight School at the airport, said "This airport is very close so we all know each other and feel for them."
Washington County Commissioner James Kercheval was among the several hundred people who attended Thursday night's reception of the Fort Detrick Alliance at the Hagerstown Regional Airport.
"I knew there was a helicopter giving rides -- I could see it out the window," Kercheval said Friday. At first he said he thought it was a Maryland State Police Medevac helicopter but was told it was a private company giving rides.
"I didn't go for a ride," Kercheval said.
Kercheval attended the gathering because of Washington County's interest in Fort Detrick and the fact many of the fort's employees are Washington County residents.
Staff writers Heather Keels and Marlo Barnhart contributed to this story.
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