SAN BERNARDINO, California (AP):

In the final few years of Tashfeen Malik's life, the people around the young woman saw her dress ever more conservatively and urge people ever more ardently to live a devout life.

For an aunt in Malik's old hometown in Pakistan, Malik's growing religious focus was one of the last things she heard about her 29-year-old niece - before last week, when she learned that her niece and her niece's husband had donned masks, hoisted assault rifles and killed 14 people in a rampage in southern California.

"I recently heard it from relatives that she has become a religious person, and she often tells people to live according to the teachings of Islam," recalled aunt Hifza Batool.

Batool spoke in the town of Karor Lal Esan, the home of Malik's family, 280 miles (450 kilometres) southwest of the Pakistani capital of Islamabad.

Malik's path from Pakistan to the bloody events of last week - when she and her husband slaughtered people gathered for a training session and holiday luncheon - remains a mystery.

FBI officials, family lawyers, and others said they know little about the housewife and mother, apart from what came to light on Friday: that Malik had pledged allegiance on Facebook to the Islamic State group as she and her America-born husband, Syed Farook, 28, launched the massacre.

The husband and wife were killed in a furious shootout with police hours after they opened fire on a gathering of Farook's colleagues from the San Bernardino County public health department, where he worked as a restaurant inspector.

The FBI said it is investigating the rampage as a terrorist attack.