Helmet-cam captures moment thief steals Brazilian man's motorbike - and is immediately shot by undercover police

Unconfirmed reports suggest the motorbike-jacker later died of his wounds

Warning: graphic footage of gun violence

Video footage has emerged from Brazil of the moment a thief tried to steal a high-performance motorbike which had stopped at traffic lights – and was immediately shot by police.

In the graphic footage captured by the theft victim’s helmet camera, two men on another bike pull up in front of him at a junction.

The man riding on the back of the bike in front pulls out a gun, and forces the covert cameraman to give up his vehicle and step aside.

As he watches on, the thief is about to pull away when he is approached by a policeman who, sitting in an unmarked car, had clearly been able to see the events as they unfolded.

A shout can be heard before the policeman fires twice, knocking the thief from the bike. By this point his accomplice has already sped away.

The video was posted to the website Live Leak, and though in a longer version the thief is still clearly alive some six or seven minutes later as policemen stand around waiting for an ambulance, the post includes unconfirmed reports in a caption saying he later died of his wounds.

Some commenters have hailed the actions of the policeman, pointing out that he himself could very easily have been shot. American user Zcotty posted: “An excellent split second decision, deadly force met with immediate deadly force.”

Others have questioned the willingness to open fire in the policeman’s response, and have linked the incident to security fears ahead if the 2014 World Cup and 2016 Olympics, both to be held in Brazil.

“Required gear for the next World Cup: a customary vuvuzela and a bulletproof jacket,” wrote one commenter.

The upcoming major sporting events have brought international attention to longstanding security issues in Brazil, among them the apparent ease and willingness with which the police will open fire.

Even fairly minor, peaceful protests have suddenly turned violent in recent weeks, while the summer’s Confederations Cup in the country was marred by a series of bloody clashes.