Moments before last week’s fatal helicopter crash on one of Kailua’s busiest streets, witnesses on the ground heard a loud metallic bang and then saw the tour craft partially breaking apart in mid-air, according to federal investigators’ preliminary report.

The rotor blades had stopped moving, according to the National Transportation Safety Board report issued Thursday.

The helicopter, a four-seat Robinson R44 model owned by local tour company Novictor Aviation, went into a steep vertical dive “with little forward motion,” the report said.

Witnesses saw part of its main rotor blade, as well as the fuel tank and pieces of plexiglass, fall from the helicopter before it crashed onto Oneawa Street near Kalolina Street at about 9:10 a.m April 29, killing the pilot and two passengers. The craft then burst into flames.

The NTSB document is an initial report as investigators continue to examine the helicopter wreckage at an undisclosed location. Novictor founder Nicole Vandelaar and Torrance, California-based Robinson Helicopter company officials are assisting the agency, according to the report.

At the time of the crash there was light rain, winds blowing at about 9 mph and an overcast sky, with broken cloud cover as low as 1,800 feet from the ground, the report said.

The crash killed pilot Joseph Berridge, 28; Ryan McAuliffe, 28, of Chicago; and Jan Burgess, 76, of Australia. All three died from multiple blunt-force injuries, according to the Honolulu Medical Examiner’s Department. Berridge had moved to Hawaii about two weeks earlier.

Helicopter noise, particularly from frequent tour flights, has been a contentious issue in certain communities across the state for decades. Last week’s crash in a crowded area has generated further scrutiny of the local industry, with state and federal lawmakers requesting more details on the number of flights, operators and crash history.

The Federal Aviation Administration controls the airspace, making it difficult for county and state leaders to restrict tour flights.

Read the NTSB report here: