"The whole thing is mind-boggling," attorney Mark Geragos told The San Francisco Chronicle. "They were out there for 30 to 35 minutes and nobody takes them seriously – especially when there was blood. It's incredible."
A zoo spokesman said police had not completed an investigation of the attack, which ended when the tiger was killed.
The big cat reportedly was on the loose more than 45 minutes.
Geragos told the Chronicle the youths had not taunted the animal and had no idea why it attacked them.
Lions and tigers will not be on exhibit when the zoo reopens Thursday, the newspaper said.
The zoo was expected to add a four-to-five foot tempered glass wall to its tiger and lion exhibits to increase the height of the protective barrier to 16 ½ feet, and may install surveillance cameras.