The New York Police Department's Street Crimes Unit has a motto its members are proud to recite: 'We own the night'. The elite plain-clothes group, which patrols some of the city's meanest streets in search of criminals with guns, has in recent years become a key weapon credited with contributing to the dramatic reduction in violent crime. But four of its members now stand accused of an inexplicable violent act of their own: the killing of an unarmed, innocent man in a hail of bullets. The death of Guinean immigrant Amadou Diallo, who died almost instantly after being hit by 19 of 41 rounds fired by the officers in the hallway of a grim Bronx apartment building, has cast a shadow over the work of New York's Finest. It has also reopened old, familiar racial wounds which continue to fester in the wake of all-too-regular instances of police brutality against black and Hispanic citizens. The Diallo case is certain to be another tough test of the traditional loyalties within the city's police, whose members often hide behind a wall of silence in order to avoid incriminating each other when their actions come under scrutiny. It also comes on the heels of the case of Abner Louima, a Haitian immigrant who hit the headlines after he accused white officers of beating him up and assaulting him sexually with a toilet plunger at a Brooklyn police station. Civil liberties groups are also asking whether the incredible success of Mayor Rudolph Giuliani's administration in cracking down on street crime has come at the expense of citizens' civil rights. Such is the outrage at the shooting of Diallo - a hard-working street vendor and practising Muslim - that Amnesty International has called for an independent inquiry, saying the incident 'raises deeply troubling questions about the use of excessive force and police brutality'. Al Sharpton, the black community activist who is known for jumping on the bandwagon of most race-related controversies, has already appeared with the family of the dead man, calling the shooting 'the worst form of police brutality'. But perhaps the most poignant commentary has come from members of the tight-knit West African community, many of whom came to the United States to escape violence back home. 'It makes you wonder whether leaving your troubled home was a mistake,' a local Liberian shopkeeper told the New York Times. 'America was supposed to be a safe haven, but if you get shot by the police, who else can you turn to?' The shooting occurred when four Street Crimes Unit officers - all of whom are white - were in an unmarked car and spotted Diallo in the hallway of his building, apparently acting suspiciously. Believing he fitted the description of a wanted rapist, they approached him and opened fire, apparently because they believed he was reaching for a gun. Since the four officers were the only witnesses - and have so far declined to answer questions about the incident - the truth about what happened remains unclear. But most observers are shocked that the officers fired 41 rounds at a man who posed no threat. The special unit was increased in size by Mayor Giuliani from 100 to 400 officers in 1996, in recognition of its role in clearing up street crime. In the past two years, it has accounted for 40 per cent of all firearms-related arrests, despite its modest size. However, its take-no-prisoners approach to policing has run into trouble on several occasions. Three of the officers involved in the latest shooting have been associated with previous shootouts, and the unit's tactics have been criticised by some judges.