SAN FRANCISCO — San Francisco Zoo workers should have believed two brothers who said a tiger was loose and had mauled their friend, but overall reacted well to the fatal Christmas Day attacks, according to the organization that accredits the nation's zoos.

The report by the Association of Zoos and Aquariums, which the zoo released in excerpts Tuesday, provided its most detailed account of the fatal mauling. The full document remains confidential between the organization and the zoo, but association spokesman Steve Feldman said the excerpts released by the zoo accurately reflected the full report.

"They've accurately summarized the findings from those documents," Feldman said. "The fact that we've maintained the zoo's accreditation also speaks for itself."

Association inspectors criticized the zoo's security supervisor for doubting two brothers, Kulbir and Paul Dhaliwal of San Jose, who said a tiger had escaped from its enclosure and attacked them and their friend.

Responding to calls that the men were at a zoo cafe seeking medical attention, the supervisor arrived to find that brothers "behaving erratically, possibly intoxicated," according to the inspection report's timeline of the incident.

The supervisor assumed there had been a fight and did not believe a tiger was free "because of the erratic and belligerent behavior of the two guests," the report said.

The 250-pound Siberian tiger, named Tatiana, already had killed 17-year-old Carlos Sousa Jr. and was roaming the zoo grounds. Minutes later, it attacked the brothers, who were kept outside the cafe by a manager who lacked a zoo radio and didn't know the tiger had escaped, the report said.

The report found that most of the zoo's workers had been sent home early for the holiday, leaving too few staffers on hand.

AZA inspectors also found that the one zookeeper who was trained as a shooter in animal escapes did not have keys to remove a shotgun from storage. He eventually retrieved the weapon with help from a veterinarian who had left for the day and returned because she had forgotten to complete a report.

The tiger was fatally shot by police about 20 minutes after the brothers first reported they had been attacked, according to police and zoo timelines.

The attacks came just over a year after the tiger devoured the arm of a zookeeper during a feeding.

"The zoo is too often chasing problems rather than proactively addressing known concerns," the report said. "This will require a shift in culture and the supervisory and maintenance staff to make it happen."