CAMBRIDGE, Mass. (AP) _ A state police helicopter crashed onto the roof of an unoccupied boathouse owned by Harvard University shortly after takeoff Wednesday, killing two police pilots and the two civilians with them.

The wreckage drew scores of people to the normally quiet banks of the Charles River, which runs along the edges of the Harvard and Massachusetts Institute of Technology campuses.

MIT maintenance worker Glenn Wilder happened to be practicing safety procedures with other members of a university rescue unit when the crash occurred.

``We lifted the fuselage up and cut them out of their seatbelts, but we couldn't get a pulse,'' Wilder said.

Witnesses said the chopper's main rotor was not spinning as the helicopter fell onto the flat roof of the one-story boathouse.

The French-made Aerospatiale AS350-B jet helicopter was skinned of its blue metallic shell and left dangling at the edge of the Harvard Yacht Club, which sits across the Charles River from the site of the Fourth of July Boston Pops concert. The club is used primarily for sailing; a larger boathouse for the Harvard crew sits about a mile upstream.

The bodies of the victims, covered by white sheets and lying next to the wreckage, could be seen from nearby buildings for three hours before they were removed.

The two troopers were identified as Paul Perry, 39, and James Mattaliano, 33. The civilians were Arthur T. Howell, 47, and Michael McCarthy, 46, both AT&T customer service engineers who had been with the company almost 30 years, company spokeswoman Robin Sayre said.

She said the two employees were assigned to a state account and were going to Norwood Airport to work on communications equipment at a state police building there.

Col. Charles Henderson, head of the state police, said it was not unusual to have civilians on board state helicopters. He refused to elaborate on the particulars of the fatal flight.

The helicopter left a helipad about two miles away at 9:30 a.m. and was traveling west when it crashed about three minutes later, Henderson said.

Larry Abeln, director of the master's program at MIT's nearby Sloan School of Management, said he heard a loud boom and saw a lot of smoke, but no flames.

``I saw the impact of this blue helicopter on the corner of the boathouse,'' Abeln said. ``I heard this huge explosion and saw half of the helicopter sticking out from the corner of the building.''