U.S. President Barack Obama said Thursday that terrorism or a workplace dispute could have motivated a couple to carry out a deadly shooting rampage at a holiday party in California that left 14 people dead and 17 others injured.
Speaking at the White House, Obama said, "It is possible this is terrorist related, but we don't know. It could be workplace violence. There may be mixed motives in all this. We don't know their motivations." But Obama added, "I can assure the American people we will get to the bottom of this," with investigators looking for clues as to their motives.
He said the carnage from Wednesday's assault on a local government social services center for developmentally disabled people in San Bernardino, California should spur lawmakers in Washington "to take basic steps to make it harder, not impossible, to get weapons."
WATCH: Obama addresses shooting rampage
Obama said "right now it's just too easy" for people to buy guns in the United States, where gun ownership is an embedded right in the country's constitution.
Obama offered his comments on the shooting after getting briefings from the country's top law enforcement officials, Attorney General Loretta Lynch and the director of the Federal Bureau of Investigation, James Comey.
Hours after Wednesday's shooting spree, police killed two suspects in a gun battle three kilometers away in the nearby town of Redlands. San Bernardino police chief Jarrod Burguan identified the shooters in the massacre as Syed Rizwan Farook, a U.S.-born, 28-year-old restaurant inspector for the local health department, and his wife or fiancee, 27-year-old Tashfeen Malik, whose nationality was not immediately known.
Burguan said the man and woman were dressed in "assault-style clothing" with ammunition attached and heavily armed with assault weapons and semiautomatic handguns when they stormed into the Inland Regional Center, located an hour away from the major U.S. city of Los Angeles.
The police chief said Farook had earlier attended the party and left after an apparent dispute and then returned to the facility that provides services for people with such disabilities as autism, cerebral palsy and epilepsy.
Authorities said the couple had not been on any U.S. terrorist watch list.
WATCH: Video from the scene in San Bernardino
'On a mission'
"They came prepared to do what they did," Burguan said, "as if they were on a mission. Based on how they were equipped, there had to be some degree of planning that went into this. I don't think they just ran home and put on these tactical clothes, grabbed guns and came back on a spur of the moment thing."
The couple had dropped off their six-month-old daughter with relatives before the attack, saying they had a doctor's appointment.
It was deadliest mass shooting in the United States since a gunman opened fire at an elementary school three years ago that left 26 children and adults dead. But it was the 355th mass shooting this year in the U.S. in which four or more people have been shot in a single incident.
Farook's brother-in-law, Farhan Khan, said he was bewildered by news of the shooting.
"Why would he do that?" Khan asked. "Why would he do something like this? I have absolutely no idea. I am in shock myself."
Hussam Ayloush, the executive director of the Muslim advocacy group Council on American-Islamic Relations, appealed to Americans to not jump to conclusions about the motives behind the rampage.
"Is it work? Is it rage-related? Is it mental illness? Is it extreme ideology?" Ayloush said. "We just don't know.
"We unequivocally condemn the horrific act that happened today," Ayloush told reporters. "We stand in solidarity in repudiating any possible ideology or mindset that could have led to such (a) horrific act."
A third person was arrested while trying to flee the shootout, but police chief Burguan said it is unclear what he was doing at the scene and was not believed to be a shooter.
Patrick Baccari, a co-worker of Farook, said he traveled to Saudi Arabia earlier this year and returned with a wife, although he did not say the woman was Malik.
This shooting comes less than a week after a gunman killed three people and wounded nine in a shooting rampage at a Planned Parenthood women's health clinic in Colorado Springs, Colorado.
In October, a gunman killed nine people at a college in Oregon and in June a white gunman killed nine black churchgoers in South Carolina.