A change came over Tashfeen Malik two or three years ago. She started dressing more conservatively, wearing a scarf that covered nearly her entire face, and became more devout in her Muslim faith, according to some who knew her in Pakistan.

But her path from there to the bloody events of this past week — when she and her husband slaughtered 14 people in a commando-style shooting rampage at a holiday luncheon — remains a mystery, with FBI officials, family lawyers and others saying they knew little about the 29-year-old Malik before the explosion of violence.

As the FBI announced Friday that it is investigating the massacre as a terrorist attack, law enforcement authorities and others offered evidence that Malik had become radicalized at some point and had shared her beliefs online.

A U.S. law enforcement official said Malik used a Facebook alias to pledge her allegiance to ISIS and its leader just before the shootings.

And a Facebook official said Malik praised ISIS in a post at 11 a.m. Wednesday, around the very moment the couple stormed a social service centre where her husband's co-workers from San Bernardino County's health department had gathered.

Hours later, she and her American-born husband, Syed Farook, 28, were killed in an SUV in a fierce shootout with police.

California Shootings, David Bowdich of FBI

David Bowdich, centre, assistant FBI director in charge of the bureau's Los Angeles office, talks to reporters during a news conference Friday, Dec. 4, 2015, in San Bernardino, Calif. The FBI said Friday it is officially investigating the mass shooting in California as an act of terrorism. (Jae C. Hong/Associated Press)

FBI Director James Comey would not discuss whether anyone affiliated with Islamic State communicated back with Malik, but he said there was no indication yet that the couple was part of a larger cell or was directed by a foreign terror organization.

If the rampage is proved to be terrorism, it would be the deadliest attack by Islamic extremists on American soil since Sept. 11, 2001.

The White House says U.S. President Barack Obama will address the nation from the Oval Office at 8 p.m. ET on Sunday about the steps the government is taking to keeping people safe after the past week's attack. 

Malik dressed more conservatively over time

Lawyers for Farook's mother and three siblings described Malik as "just a housewife" who was quiet like her husband and strictly followed Muslim custom. She wore traditional clothing that covered her face so her male relatives didn't even know what she looked like, according to the lawyers.

Malik arrived in the U.S. in 2014 on a Pakistani passport and a fiancée visa but had spent extended periods of time in Saudi Arabia. Farook, a restaurant inspector for the county, was born in Chicago to Pakistani parents and raised in Southern California. The couple had a six-month-old daughter, now in the care of social service workers.

Malik started studying pharmacy at Bahauddin Zakariya University in the Pakistani city of Multan in 2012, said the university's vice chancellor, Tahir Amin. It was not immediately clear whether she graduated.

CALIFORNIA-SHOOTING/

Prayer beads are shown inside the home of suspects Syed Rizwan Farook and Tashfeen Malik in Redlands, Calif. (Mario Anzuon/Reuters)

A maid who worked in the Multan home where Malik lived said she would travel back to Saudi Arabia to be with her family when school was out. During her time in Multan, her style of dress became more conservative over time, the maid said.

The maid said Malik initially wore a scarf that covered her head but not her face. A year before she got married, she started to dress more conservatively and began wearing a scarf that covered all but her nose and eyes, the maid said. The maid spoke on condition of anonymity because did not want to jeopardize her employment with the family.

ISIS calls couple 'supporters'

A relative of Malik's in Pakistan likewise said the young woman apparently became a more devoted follower of the Muslim faith in the past few years.

Hifza Batool told The Associated Press on Saturday that other relatives have said that Malik, who was her step-niece, used to wear Western clothes but began wearing the hijab head covering or the all-covering burqa donned by conservative Muslim women about three years ago.

"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," said Batool, a teacher who lives in Karor Lal Esan, about 280 miles southwest of the Pakistani capital of Islamabad.

Attorneys for family San Bernardino shooter speak out1:06

The Farook family attorneys, David Chesley and Mohammad Abuershaid, said none of his relatives had any indication either Farook or his wife held extremist views.

"If the most evidence there is to any affiliation is a Facebook account under another person's name ... then that's hardly anything at all," Chesley said.

He and Abuershaid said the family was shocked by the attack and mourns for the victims. They cautioned against rushing to judgment on their motivations.

An ISIS-affiliated news service called Malik and Farook "supporters" of their Islamist cause but stopped short of claiming responsibility for the attack.

The U.S. official and Facebook figure who discussed Malik's postings spoke on condition of anonymity because they were not authorized to talk about the matter publicly.

The Facebook official said the company discovered Wednesday's post the next day, removed the profile from public view and reported its contents to law enforcement.

FBI raids former Farook family home

Early Saturday, authorities with guns drawn raided a home next door to the house where Farook's family used to live in Riverside, Calif., breaking windows and using a cutting torch to get into the garage, neighbours said.

The FBI would not say what it was looking for, but a neighbour said an old friend of Farook's lives there. More than three years ago, that person bought the two assault rifles later used in the shooting, but authorities haven't been able to talk to him because he checked himself into a mental hospital after the attack, said a law enforcement official who was not allowed to discuss the investigation and spoke on condition of anonymity.

The FBI has said the man is not a suspect in shootings, though they want to question him.

California Shootings

A note, flowers and candles are placed at a makeshift memorial in San Bernardino, Calif., on Friday, Dec. 4, 2015. (Jae C. Hong/AP)

Farook stopped attending mosque 3 weeks ago

Farook went to the Dar Al Uloom Al Islamiyah of America mosque in San Bernardino every day but abruptly stopped coming three weeks ago. While many members said they knew Farook and described him as quiet and very studious, "no one knows anything about his wife," said Mahmood Nadvi, son of the mosque's founder.

Law enforcement officials have long warned that Americans acting in sympathy with Islamic extremists — though not on direct orders — could launch an attack inside the U.S. ISIS in particular has urged sympathizers worldwide to commit violence in their countries.

Since March 2014, 71 people have been charged in the U.S. in connection with supporting IS, including 56 this year, according to a recent report from the George Washington University Program on Extremism. Though most are men, "women are taking an increasingly prominent role in the jihadist world," the report said.