Grave fears for British outback tourist

Police released this identity photo of the gunman in a bid to find him and tourist Peter Falconio

By CNN's Kirsty Alfredson

DARWIN, Australia (CNN) -- Australian police say they have received more than 50 calls following the release of an identity kit photo of a gunman suspected of murdering a 28-year-old English tourist and abducting his girlfriend.

Tourist Peter Falconio and his 27-year-old girlfriend Joanne Lees were holidaying in the Northern Territory when they stopped on Saturday night to help a man who they thought was a stranded motorist.

After Falconio got out of their camper van to speak to the driver, Joanne Lees heard a shot. She was then abducted at gunpoint, and bound and gagged, she told police.

She managed to escape but spent a terrifying six hours hiding in scrub with her hands bound while her captor searched for her.

Blood found at scene

Lees has been helping police with their investigations, providing a detailed description of the man who, was driving a white 4-wheel drive utility vehicle.

Aboriginal trackers have been searching the scene at Barrow Creek where police say blood has been found. They are not releasing forensic tests on the blood but one Australian TV station is reporting it is Falconio's.

Roadblocks remain in place and interstate police are on alert. There are more than 100 police involved in the search utilizing planes, helicopters and vehicles.

Police say they hold grave fears for Peter Falconio, whose brother and father are traveling to Australia.

The British couple were traveling together across Australia

British newspapers are reporting the "outback nightmare" saying the families back home are "going through hell".

A tearful Luciano Falconio told the media that his son was a "good guy".

"I hope they catch the person who did it," he said. "My son did not deserve this."

The Times newspaper reported that the owner of the Barrow Creek Road House where Lees fled after her ordeal, described her as a "gutsy lady".

"She said he bound her hands in front of her and so she was able to undo her leg strappings and make her getaway," he said.

"She was really traumatized when she walked in here after being given a lift by a passing lorry driver, but she's a wonderful gutsy lady."