(CNN) -- Philippine authorities acknowledged for the first time Thursday that some of the tourists taken hostage in a bus standoff last month may have been shot by police in the bungled rescue operation.
Until now, Manila police had said officers did not kill any of the hostages. The driver of the bus also told investigators that the hostage-taker shot each of the passengers at close range.
But on Thursday, Justice Secretary Leila de Lima -- who is leading an official inquiry into the August 23 incident -- told reporters there was a "big possibility" that some of the passengers in the bus died in "friendly fire."
Lima said that forensic findings seemed to contradict the driver's account. The number of bullets found in the bus did not match the number from the hostage-taker's gun, she said.
"That's what makes Secretary de Lima's statement more crucial," said Eduardo Lingao of the Philippine Center for Investigative Journalism. "Earlier, the Philippine national police chief shut the door at the possibility of friendly fire. Now she is saying, 'No, no, no, there is a big chance some of them were hit.'
"In effect she is saying, 'We shouldn't have ruled this out.' She is opening the door that the police chief had shut."
Former police officer Rolando Mendoza, who was apparently upset about having lost his job, took hostage a busload of tourists from Hong Kong.
Witnesses said Mendoza was initially willing to cooperate, but he was shot dead by police after authorities say he became violent and started shooting hostages.
Four men and four women were killed in the standoff. One passenger was critically wounded, and six others were hospitalized with less serious injuries.
Rodolfo Matibay, district director of Manila police, took responsibility for how the incident was handled, saying he ordered the police assault on the bus, according to Gen. Leocaldo Santiago, regional director of Manila police.
He has been placed on administrative leave, while the case is being investigated.
The gunman had previously released nine of the hostages, including a mother and her three children, a man with diabetes and two photographers. The bus driver escaped.
Earlier, Santiago said police killed none of the hostages, though a ballistics investigation has yet to be completed.
The deadly standoff unfolded live on television, which the gunman was able to watch on a monitor on the bus.
Santiago blamed the live broadcasts for contributing to the violence, as the standoff quickly deteriorated, while police surrounded the vehicle.
"We do not want to pass sweeping judgment or make early conclusions except to say that our intention to peacefully end this hostage drama was spoiled when the hostage-taker suddenly exhibited violent behavior and began shooting the hostages," Philippine National Police Chief Director Gen. Jesus A. Verzosa said the day after the standoff.
National police said officials noted "some observations and defects during their close monitoring of the unfolding events."
The statement did not provide details. However, it listed poor handling of the hostage negotiations; inadequate capability, skills, equipment and planning of the assault team; improper crowd control; inadequate training and competence of the assault team leader; and noncompliance to media relations procedures in hostage situations.
"The investigation has got to find out what was the turning point? What happened?" Richard Gordon, chairman of the Philippine National Red Cross, said last month.
Gordon said survivors said the situation inside the bus changed dramatically toward the end of the 10-hour standoff.
"Apparently the man went berserk. He was telling everybody he was not going to harm [them]. ... He said that nobody's going to get harmed. He said that he was probably going to die but not the hostages," he said.
Santiago said that Mendoza's family members spoke with him early in the standoff and that he appeared "very reasonable and very psychologically stable."
Mendoza was a decorated police officer, winning several accolades. But his career spiraled downward when he was dismissed a year ago for extortion, Manila Vice Mayor Isko Moreno said, and he wanted his motion for reconsideration to be heard.
Moreno said that Mendoza's brother was arrested during the standoff because he was "guilty of conspiring with his brother" and allegedly helped instigate the shooting.
Gordon said the brother's arrest may have pushed the gunman over the edge.
"When he saw his brother getting accosted by the policemen, he went berserk and he started firing," he said.