Estranged relatives of a Pakistani woman involved in a mass shooting in California spoke on Sunday of their shame at her crimes, as former classmates and teachers painted a picture of a quiet, religiously conservative student.

Tashfeen Malik, 29, and her husband, Syed Farook, 28, gunned down 14 people at a social services center in San Bernardino, an act praised by the Islamic State group who hailed the couple as "soldiers" of its self-proclaimed caliphate.

According to her uncle, Malik Ahmed Ali Aulakh, who is a former provincial minister, Tashfeen was born in the village of Karor Lal Esan in the central province of Punjab but moved to Saudi Arabia around 1989.

"We are ashamed and shocked about this act done by our niece - why did she do something so gruesome? We can't believe it," he said.

The southern region of Punjab from which Tashfeen hailed has long been associated with Sufism, a mystical form of Islam whose adherents worship with song and dance, attend shrines and devote themselves to historic saints - practices viewed as heretical by more-orthodox Muslims.

It is still not clear where Tashfeen became radicalized, but by the time she returned to Pakistan in 2007 to pursue a degree in pharmacology at the Bahauddin Zakariya University that lasted till 2013, she was devoutly religious and wore a veil, according to former instructors.

"She was not outspoken or ultramodern but she was religious minded, polite and submissive," said Dr Khalid Hussain Janbaz, chair of the pharmacy department.