SAN BERNARDINO, California: The couple suspected of killing 14 people at a holiday party in California amassed thousands of rounds of ammunition and a dozen pipe bombs, and authorities on Thursday sought to determine their motives and whether they had links to Islamist militants.
Syed Rizwan Farook, 28, and Tashfeen Malik, 27, his wife and mother of his 6-month-old daughter, were killed in a shootout with police five hours after Wednesday's massacre at the Inland Regional Centre social services agency in the city of San Bernardino.
Twenty-one people were wounded in the shooting, which ranks as the deadliest instance of US gun violence in three years.
San Bernardino Police Chief Jarrod Burguan said at a Thursday news conference that the search of a townhouse leased by Farook and Malik in the nearby community of Redlands turned up flash drives, computers and cellphones.
Officials in Washington familiar with the investigation said so far there was no hard evidence of a direct connection between the shooters and any militant group abroad, but the electronics would be checked to see if the couple had been browsing on jihadist websites or social media.
CNN, citing law enforcement sources, said Farook had been "radicalised" and had been in touch through telephone and social media with more than one international terrorism suspect who was being investigated by the FBI.
USA Today, citing a federal law enforcement source, reported investigators were examining Farook's contacts with an undisclosed number of people whose suspected ties to radical ideology have become known to the FBI.
Officials from President Barack Obama to Police Chief Burguan said the attack may have been an act of terrorism but that questions of motive remained unanswered.
"It is possible that this was terrorist-related. But we don't know," Obama told reporters. "It is also possible that this was workplace-related."
Farook, a US citizen, was born in Illinois, the son of Pakistani immigrants, according to Hussam Ayloush, who heads the Los Angeles area chapter of the Muslim advocacy group Council on American-Islamic Relations (CAIR).
David Bowdich, FBI assistant director in Los Angeles, said the couple had entered the United States in July 2014 after a trip abroad that included Pakistan and perhaps other countries.
He said Malik was admitted to the United State on a K-1 "fiancee visa" and was travelling on a Pakistani passport.
Farook, who according to public records worked as an health inspector for San Bernardino County, did not have a criminal record, Burguan said.
Police cited witness accounts that Farook had been attending the holiday party thrown for employees of the county Environmental Health Department but stormed out in anger. He then returned with Malik armed with assault gear and opened fire.
Burguan said they sprayed the room with 65 to 70 rounds.
MORE WEAPONS, BOMB-MAKING EQUIPMENT AT HOUSE
Burguan said the couple had two assault-style rifles, two semi-automatic handguns and 1,600 rounds of ammunition in their rented sport utility vehicle, when they were killed. At the townhouse, police found another 4,500 rounds, 12 pipe bombs and bomb-making equipment.
The guns were legally purchased in the United States, said Meredith Davis, a spokeswoman for the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF).
Burguan said Farook bought the two handguns. The rifles were purchased by someone else, who Davis said was not linked to the investigation.
In addition to sparking further debate on gun control laws, the latest mass slaying in the United States came with much of the world on edge following the Nov. 13 attacks in Paris by Islamic State militants that killed 130 people.
Ayloush appealed to the public not to jump to conclusions about the motives behind the San Bernardino attack. He said he was concerned about a backlash against the broader Muslim community in view of the rise of Islamic State and some opposition among politicians and the public in the United States over U.S. plans to accept Syrian war refugees.
"We're living in a very difficult time," he told CNN. "There's a lot of Islamophobia out there, a lot of anti-Muslim sentiment, fuelled by pundits here and there trying to blame a whole community for the acts of a few."
Nizaam Ali, a 23-year-old college student who said he knew Farook from mosque, said Farook prayed two to three times a week during his lunch break at the Dar Al Uloom Al Islamiyah of America mosque in San Bernardino. Ali said he had not seen any signs of radicalisation or extremism.
Farook told Ali that he married his wife, whom he met online, in July 2014. Ali added that Farook's wife wore the niqab, a scarf that covers most of the face, which was something Farook had mentioned he liked about her.
OBAMA REITERATES CALL FOR GUN LAW REFORM
The San Bernardino rampage was the deadliest US shooting incident since the December 2012 massacre at Sandy Hook Elementary School in Newtown, Connecticut in which 27 people, including the gunman, were killed.
There have been more than 350 shootings this year in which four or more people were wounded or killed in the United States, according to the crowd-sourced website shootingtracker.com, which keeps a running tally of US gun violence.
"I don't think any community is immune," San Bernardino Mayor Carey Davis told CBS. "Certainly, we don't anticipate that kind of thing happening here. It was a shock."
Davis, whose largely working-class city is 60 miles (100 km) east of Los Angeles, said on Twitter he had a "heartfelt conversation" about the killings with Obama, who used the incident to make another call for gun law reform to reduce the likelihood of mass shootings.
"We're going to have to, I think, search ourselves as a society to make sure that we can take the basic steps that would make it harder - not impossible but harder - for individuals to get access to weapons," Obama said at the White House.
He ordered flags to be flown at half-staff in memory of the shooting victims.
Ten people remained hospitalized at two hospitals on Thursday - two in critical but stable condition, five in fair condition and three in good condition, the hospitals said.
© Thomson Reuters 2015