A helicopter crashed through the roof of a Kenosha, Wis., home in a residential neighborhood early Sunday morning, rolling down the second-story staircase and narrowly missing a sleeping family of five before coming to a standstill in a neighbor’s lawn across the street, police said.

No one in the house was injured during the 5:30 a.m. crash, but both people in the helicopter were killed, Kenosha Police Sgt. Cindy Fredericksen said. The identities of the deceased were not immediately released.

The cause of the crash was not immediately known, but Fredericksen said it appeared the helicopter had lurched onto its side as it crashed into the home in the pre-dawn fog, causing the whirring blades to slice through the roof and sending the helicopter tumbling down the stairs and out the front door. It caught fire as it exited the home and rolled onto the lawn.

Federal Aviation Administration officials were investigating the crash, officials said. FAA spokesman Tony Molinaro said the helicopter, a Robinson R44, was operated by Midwestern Air Services out of Kenosha, and had not filed a flight plan prior to departure. The pilot was en route from an undisclosed private airport in Chicago to an airport in Kenosha about two miles from where the accident occurred, police said.

Because the crash involved fatalities, FAA investigators planned to turn over their findings to the National Transportation Safety Board, Molinaro said.

James Meomartino, a neighbor, said that just before the crash, a strange, loud beeping noise above their heads startled him and his wife awake.

“It was the warning instrument – like the annoying noise when you don’t put your seatbelt on,” Meomartino said.

They then heard a loud boom. Meomartino ran outside to find the helicopter on fire in an adjacent yard, he said.

Meomartino said he ran to help the family – a husband, wife, and three children – escape from the rubble, bringing them over to his house.

“They were in shock,” Meomartino said. “But they were very calm. There was no major problem because they were all alive.”

Witnesses said the house did not catch fire, but the helicopter left a gaping hole in the back of the roof and the propeller sliced it in half. The front door was blown off and in the yard. The windows and frame of the house pulled away as if the house was swelling.

Neighbors marveled that no one on the ground was hit. The neighborhood is a quintessential subdivision with hundreds of homes, many built only 15 feet apart, with narrow streets and an elementary school in the center.

At noon Sunday, the neighborhood was thick with traffic. People headed to garage sales and picnics, and onlookers with cameras waited at the end of 97th Avenue, several blocks of which had been roped off by police.

Inside the roped-off area, firefighters spent the morning cleaning fuel that had spilled onto the street. Children on bicycles called out to their friends and pointed as flatbed trailers carrying the helicopter’s charred metal and twisted propeller pulled away.

“It’s bad,” said Lucille Berry, one of a small crowd of onlookers armed with cameras who were standing beyond a police barricade. “I wouldn’t have wanted to be in that house.”

John Parrish, who owns Midwest Helicopter in Kenosha, said he went to the crash site about half an hour after the accident, when the fog was just beginning to lift. He said he thought the poor visibility may have contributed to the accident.

“These aircraft are not made to fly in this weather,” Parrish said.