A new report by the accreditation agency for the nation's zoos chides San Francisco Zoo workers for some missteps in handling a Christmas Day tiger attack, but said their overall response was "impressive."

The report by the Association of Zoos and Aquariums, which the zoo released in excerpts Tuesday, represents its most detailed account of the fatal mauling. The full document remains confidential between the organization and the zoo.

In the report, AZA 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 "are behaving erratically, possibly intoxicated," according to the inspection report's timeline of the incident.

The supervisor assumed there had been a fight and "does not believe that a big cat is out because of the erratic and belligerent behavior of the two guests," the report said.

At the time, 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 a tiger had escaped, the report said.

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

AZA inspectors also found that the one zookeeper on the scene who was trained as a shooter in animal escapes did not have keys to where a shotgun was stored. He was only able to retrieve the weapon with the help of 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 December attacks came just over a year after the same 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."

AZA 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."