The Philippines will hold a "thorough investigation" into how eight Hong Kong tourists were killed while they were being held hostage on a bus in Manila, President Benigno Aquino says.
Survivors and experts have criticised the police for being indecisive and slow in their handling of the crisis.
The day-long siege ended when police marksmen shot and killed the gunman, who was a disgruntled ex-policeman.
In the last hour of the siege, police failed in an attempt to board the bus.
They were forced back by gunfire from the inside of the vehicle.
Almost one hour later, they managed to get on board the bus. By that time, the gunman had been killed along with eight of the 15 passengers.
"We want a thorough investigation of everything that transpired," Mr Aquino told a news conference.
He defended the actions of the police at the scene, saying the gunman, identified as 55-year-old former senior inspector Rolando Mendoza, had not shown any sign of wanting to kill the hostages.
But when asked if he was entirely satisfied with the police, he said: "How can you be satisfied if there were some people who were killed?"
His comments came amid rising anger at the handling of the crisis.
One of the survivors, who identified herself only as Mrs Leung, told reporters: "Why was there no one to help us after so many hours?"
She said her husband had been killed trying to stop the gunman from shooting other passengers.
"I miss him. I actually really wanted to die with him. But I think of my children," she said.
Hong Kong's leader Donald Tsang also criticised the way the siege was dealt with.
And security analysts questioned whether the police were trained to handle such a situations.
Frederic Gallois, who once commanded France's elite hostage rescue unit, told the AFP news agency that the police operation was "badly prepared and risky".
Mr Gallois said the officers involved "visibly lacked adequate equipment and tactical competence".
Earlier, police spokesman Colonel Nelson Yabut said the police had initially been forced to retreat because an officer was shot and injured.
"On our first assault, Captain Mendoza was sprawled in the middle of the aisle and shot one of our operatives. On our second assault we killed him," said Col Yabut.
The gunman had spent almost three decades with Manila's police force, but was sacked earlier this year over claims of extortion.
During the hostage crisis, he posted signs with his demands on the bus windows - the main one urging the police force to reinstate him.
The gunman had boarded the bus at Luneta Park in central Manila, and the hostage drama played out across the eight-lane road inside the park.
In all, 22 Hong Kong tourists were taken hostage along with three Filipinos - a driver, a guide and a photographer.
Nine people were freed after initial negotiations, and the driver fled, leaving 15 hostages on board until the end of the siege.