Two people have died after a light plane crashed into a river during an air show in Perth, Australia, on Thursday (26 January). The incident took place in front of thousands of spectators who had gathered to watch Australia Day celebrations on the river front.

Horrific footage of the plane nosediving emerged on social media, which showed a Grumman G-73 Mallard seaplane flying above the Swan River in Perth. Within a few minutes, the aircraft went down, killing the only people on board.

The victims have been identified as pilot Peter Lynch, 52, and his passenger and partner Endah Cakrawati, 30. He was known as a "very experienced" pilot, Western Australia Police said.

"Thank God it went down in the water where it went down -- that was one of my first thoughts," WA Police Acting Commissioner Stephen Brown told reporters in Perth on Friday.

"That was the clear waterway that Peter was flying over and not too far away on the foreshore are thousands of people. And further to the west was quite a large group of members of the public on their boats," Channel News Asia quoted Brown as saying.

Aviation experts are said to be confused over what might have caused the plane to crash. The Australian Transport Safety Bureau said it could take them several months to complete investigation into the accident. However, a preliminary update is expected to be delivered within 30 days.

The Civil Aviation Safety Authority (Casa) said air display over public gatherings or boats on the water are usually not permitted. But it gave special permission for Lynch to fly his seaplane, which had the capacity to land even on water.

"Under the regulations, except during take-off and landing, or where specifically approved as part of the program of events, the minimum height at which any aircraft may operate is 500 feet above ground level," the Australian Broadcasting Corporation cited a Casa spokeswoman as saying.

STATEMENT FROM THE GREAT EASTERN FLY IN COMMITTEE REGARDS VH-CQAIt is with great sadness as we try to come to terms...

Posted by Great Eastern Fly-In Evans Head - Australia's Friendliest Flying Event on Thursday, January 26, 2017

"Air displays over built-up [suburban] areas, public gatherings and vessels on the surface of a body of water are not normally approved. These rules ensure the safety of the public and those involved in the flying display," the spokeswoman added.

Passengers were not allowed to be on board the plane during the air show, although each pilot was permitted to carry an observer.

Local media reported that Lynch was an experienced pilot and his aircraft was in a good condition. Tributes are pouring in for the pilot and his girlfriend.

The air show was part of the celebrations that included fireworks in the evening. But the events were cancelled after the accident. The show was expected to attract more than 300,000 spectators.

Australia Day plane crash
The Australian Transport Safety Bureau said it could take them several months to complete investigation into an accident during Australia Day celebration on 26 January that killed two ~ representational image only ROBERTO SCHMIDT/AFP/Getty Images