• Army helicopter shot at while rescueing refugees stranded in New Orleans
• Thousands of National Guards taken off rescue duties to tackle looting in city
• Bush pledges $10bn in aid as city reported to be running out of supplies
"The truth is, a terrible tragedy like this brings out the best in most people, and brings out the worst in some people" - Haley Barbour, Mississippi governor
Story in full THE aftermath of Hurricane Katrina turned from tragedy to anarchy yesterday, as violence and looting threatened to derail efforts to help the hundreds of thousands of people displaced from their homes and struggling to survive in appalling conditions.
Amid scenes of utter chaos, a military helicopter came under fire as it tried to lift refugees from New Orleans' Superdome sports stadium, while a hospital was abandoned after an armed gang held up a supply lorry bringing in food, water and medical supplies.
With the city likely to be uninhabitable for months, the death toll possibly running into thousands and the threat of disease from the dead bodies floating among the wreckage becoming a serious problem, relief operations should have taken priority.
Instead, thousands of National Guard troops in armoured vehicles had to be dispatched to the city and hundreds of police officers taken off search and rescue operations to tackle the looting.
"The truth is, a terrible tragedy like this brings out the best in most people, and brings out the worst in some people," said Haley Barbour, the governor of neighbouring Mississippi, vowing to deal with looters in his state as "ruthlessly as we can get our hands on them".
The US president, George Bush, who is due to visit the area today, warned there should be "zero tolerance" for those breaking the law during an emergency situation.
In a televised statement last night, the president said aid was on the way. "This is an agonising time for the people of the Gulf Coast," Mr Bush said as he stood with the two former presidents, George Bush Snr and Bill Clinton, in the White House.
"We're united in our determination to help the good people who have been hit by this hurricane," the president said as officials announced the administration intended to provide $10 billion (5.5 billion) to cover immediate relief needs.
But images of suffering continued to haunt the American public. Television crews were proving the only communication channels in the worst-hit areas.
CNN journalist Kyra Phillips said: "Where are the resources? We are not seeing these individuals in action. People are dying, we are seeing pictures of people dying and bodies on the streets."
Ray Nagin, the mayor of New Orleans, issued an urgent plea for relief of his flooded city, highlighting the plight of people stranded at its convention centre. "This is a desperate SOS," he said. "Right now we are out of resources at the convention centre and don't anticipate enough buses.
"The convention centre is unsanitary and unsafe, and we are running out of supplies for 15,000 to 25,000 people."
As many as 30,000 National Guard troops are expected to be mobilised soon, and the US Navy is sending the aircraft carrier Harry S Truman to help with rescue efforts.
But just as in Iraq in the first days after the fall of Saddam Hussein, the US authorities appeared unprepared for the scale of the looting.
The most serious incident came when shots were fired at a military helicopter.
As many as 60,000 people had gathered at the Superdome for shelter, but Richard Zeuschlag, an ambulance official, said rescue operations had been suspended until control could be regained.
Earlier, a medical evacuation helicopter aborted its landing at a hospital in the outlying town of Kenner, when the pilot reported that 100 people were on the landing pad, some of them with guns. "He was frightened and would not land," said Mr Zeuschlag.
As tempers flared, a man shot his sisters dead in an argument over a bag of ice. Dozens of car-jackings were reported, including that of a nursing home bus.
Kathleen Blanco, the governor of Louisiana, despaired at the breakdown in law and order. "It's intolerable," she said.