Members of the Baker’s Dozen a cappella group sustained serious injuries when they were attacked at a house party in San Francisco, Calif., during their winter tour.

At a New Year’s Eve party honoring the all-male singing group after a performance, two uninvited guests entered the premises and began insulting and punching the students, attempting to provoke them into fighting, said Sharyar Aziz ’74, the father of a group member. As the Baker’s Dozen members left the party after midnight, more assailants arrived in two vehicles and proceeded to harass and throw beer bottles at the students. Some of the suspects — identified by those at the party as the sons of a prominent local family — were taken into custody but subsequently released, and no arrests have been made.

Several students sustained injuries including concussions, black eyes, and other bodily bruises. When the additional group of assailants arrived, the violence quickly escalated, and group member Sharyar Aziz ’10 was thrown to the ground and kicked repeatedly. His jaw was broken in two places, requiring surgery to repair the damage, his father said. Aziz’s jaw will be wired shut for eight weeks.

Members of the Baker’s Dozen declined to comment on the incident.

Yale College Dean Peter Salovey said he has been “shocked and appalled” to learn about the details of the attack as they have surfaced. Salovey said the University has contacted the members of the Baker’s Dozen to offer them support and is making efforts to ensure that Aziz’s return to campus is as smooth as possible.

Reno Rapagnani, the owner of the house in which the party took place, said the violence seemed to erupt over a dispute between two rival college preparatory schools, St. Ignatius and Sacred Heart. The party was hosted by Rapagnani’s daughter Rose and Stephanie Soderborg ’09, both St. Ignatius alumni. Graduates from Sacred Heart interrupted the event, harassing members of the Baker’s Dozen for their formal dress and for the fact that they are not from San Francisco.

The Yale students decided to leave the party to avoid further conflict, Rapagnani said, but one of the uninvited guests called in more assailants, who drove up and attacked the students while they were walking back to the home in which they were staying nearby.

The San Francisco Police Department took the suspects into custody but subsequently released them without charges. Whitney Leigh, the Aziz family’s lawyer, said that although the police are now moving more quickly on the case, he found certain aspects of the handling of the situation “deeply troubling.”

“The apparent release of the individuals who were detained initially did not comport with normal police procedures,” he said.

Leigh said he hopes arrests will be made in the near future and that the charges, given the nature of the injuries sustained, will include multiple felonies.

But SFPD Lt. Leroy Lindo said the department is opting for a “slow, methodical approach” because of the number of people involved in the case. Lindo said the suspects were released from custody because it could not be immediately proven that they had assaulted the Yale students.

“We’re not going to be premature based on someone wanting a resolution to the case,” he said.

Lindo said the police are making progress on the case, which has erupted into a “wildfire with rumors and innuendos.”

The elder Aziz said he believes that “small town politics” likely prevented the San Francisco police department from taking swifter action on the case initially. Some of the suspects are the sons of a prominent area pediatrician, he said, and have a local reputation for violence.

Aziz is expected to make a full recovery, but his jaw is permanently fitted with titanium and he will stay on a liquid diet for eight weeks. His injuries will prevent him from singing with the Baker’s Dozen or competing on the varsity squash team through the duration of his recovery.

Dan Toubolets ’08, the Baker’s Dozen winter tour manager, said the group will continue its tour of California and is scheduled to return to New Haven on Jan. 14.