This from CNN today, in reference to allegations that Tatiana–the Siberan tiger who escaped her enclosure–may have been taunted prior to the attack:

A source close to the investigation said the rock found in the habitat measured 9 inches, and a tree branch and pine cones were found that came from trees that were not near the tiger’s enclosure.

Singer said zoo employees also alerted police to an empty vodka bottle in the car in which the young men came to the zoo.

The two brothers who were injured in the attack have a police record, and have been uncooperative with police. In the hours following the attack, they refused to identify Sousa as the person that had been killed. update: In this article in the Chronicle, a witness says that she saw four boys at the tiger pen, three of whom were taunting Tatiana–throwing things and roaring at her. According to the witness, Carlos Sousa, Jr., the boy who was killed in the attack, was not engaging in this activity, and in fact seemed apologetic that his friends were doing so. But this leaves the question–is there a third boy the brothers are protecting?

Brothers cooperating. Update, Jan. 7, from the San Francisco Chronicle
“San Francisco Police Inspector Valerie Matthews said the investigation had found no evidence that Paul and Kulbir Dhaliwal taunted a 300-pound tiger that apparently scaled a 12½ foot wall surrounding its enclosure… Matthews also said the Dhaliwals were cooperative with investigators.” The brothers will not be charged.