Washington: An arsenal of explosives and ammunition has been found at the home of a Chicago-born health worker and his Pakistani wife who killed 14 people and injured 21 others during a holiday party in California.
Chicago born Syed Rizwan Farook, 28, and Tashfeen Malik, 27, his Pakistani wife in the US. on a visa, were both dressed in tactical gear and armed with rifles, handguns and multiple ammunition magazines for the attack, media reports said.
As they strode into an event for county workers in San Bernardino Wednesday morning, the couple opened fire, spraying 65 to 75 rounds and leaving behind an unexploded pipe bomb before fleeing in a rented black Ford Expedition.
Police has found 12 'pipe bomb-type devices' at the suspect couple's home in Redlands, along with thousands of rounds of ammunition.
Another set of three pipe bombs combined into one - and designed to be triggered by remote control from a car, although the device apparently malfunctioned - was also found at the scene of the mass shooting, the Washington Post reported citing San Bernardino Police Chief Jarrod Burguan.
Investigators are still looking for a motive behind the deadliest US mass shooting since the Sandy Hook Elementary School massacre of the innocents on Dec 14, 2012 when a gunman shot 20 children and 6 adult staff members in Newtown Connecticut.
Officials said the two attackers were killed after nearly two dozen police officers engaged in a firefight with them.
Police also found more than 1,600 rounds of ammunition on the attackers, suggesting they were prepared for a long siege.
Police say they had recovered four weapons: Two assault rifles and two 9mm pistols, all of which were legally purchased, according to the Bureau of Alcohol, Tobacco, Firearms and Explosives.
"We do not know the motive. ... It would be irresponsible of me and be way too early to speculate on motive," said David Bowdich, assistant director in charge of the FBI in Los Angeles.
"There was obviously a mission here," Bowdich said. "We do not know why. We do not know if this was the intended target or something triggered him."
NBC News citing authorities said that Farook appeared to have been radicalised. They said he had been in touch with people in the Los Angeles area who have expressed jihadist-oriented views.
Citing intelligence sources, NBC News said that Farook appeared to have been in some form of communication with people overseas who are persons of interest to U.S. authorities.
Farook travelled to Saudi Arabia at least twice, in 2013 and 2014, acquaintances and Saudi officials told NBC News.
In 2013, he went on Umrah, a pilgrimage to Mecca. Nazeem Ali, 23, who attended Dar-Al-Uloom Al-Islamia mosque in Muscoy, a suburb of San Bernardino, with Farook, said Farook told him that he planned to meet the fiancée he had met online - Malik - and to get married at the Black Stone in the Grand Mosque of Mecca.
In May, Farook and Malik had a baby, whom they left with Farook's mother, claiming they they had a doctor's appointment, said Farhan Khan, Farook's brother-in-law.
A profile under the user name "farooksyed49" on the dating website iMilap.com featured a picture of Farook, which Khan confirmed was his brother-in-law. It said the user was Muslim American born in Chicago.