Sure enough, Daniel Garcia Zarraga soon came lunging at them with a glinting metallic object. Not until an officer had shot him through the ribs and killed him did the police realise the object was no knife, but a ballpoint pen.
That may sound as if it is an isolated incident of an officer losing his cool, but it isn't. A month ago, two Los Angeles Police Department officers stopped a 50-year-old homeless woman, Margaret Mitchell, in Hollywood to establish whether she had stolen her shopping trolley. Moments later, they shot her dead, claiming she had made life-threatening gestures with a screwdriver.
And in March, a man with a history of mental illness, Gus Henry Woods, was also killed by a police bullet after he threatened officers with a thin metal rod that he had been using to scratch the side of his own car.
In each case the LAPD could claim the victim failed to heed warnings and was acting in an aggressive manner. But, taken together, these incidents are proving to be a public relations nightmare for a police force still smarting from the aftershocks of the LA riots of seven years ago. The fact that Mr Zarraga was Hispanic and Ms Mitchell black has revived all the old accusations that the LAPD not only shoots first and asks questions later, but does so out of racist venom.
The Mitchell killing has raised the most heated passions, largely because it happened in daylight in a busy neighbourhood where the victim was well known to shop- owners. The LAPD has struggled to explain convincingly why two burly officers felt the need to resort to deadly force against a frail woman, even if they were confronted with a 13-inch screwdriver as they claim.
With spontaneous demonstrations at the site of Ms Mitchell's killing and national civil rights figures weighing in with accusations of gratuitous brutality, the LAPD finds itself struggling with the demons of its past at a time when many in Los Angeles had hoped that the force had taken a turn for the better.
Since the 1992 riots, which were triggered by the beating of Rodney King, a black motorist, by four white police officers, the LAPD has had two successive African Americans as its chief and been subject to greater scrutiny. Bernard Parks, chief since 1997, has been praised for cracking down on abuses in the ranks. But there have also been worrying signs of complacency. At the beginning of the year Katherine Mader, the civilian inspector general responsible for investigating accusations of police abuse, left her post, complaining that policemen were not being allowed to co-operate in confidence. Edith Perez, the city's liaison officer with the LAPD, was accused of being so close to Chief Parks that she felt unable to criticise him.
This has been a bad year for police shootings in southern California generally. Just east of Los Angeles, an 18-year-old black student was shot dead after his car was pulled over by police. And in Riverside, a young black girl, Tyisha Miller, was pumped full of bullets in January after police discovered her lying unconscious in a car at a petrol station in the middle of the night with a pistol on her lap. The Miller case has provoked demonstration after demonstration, particularly after the district attorney chose not to press charges against the officers involved. The four have since been fired, for unspecified reasons.Reuse content