A composite photo of all 14 victims from the San Bernardino shooting rampage. They are top row left: Robert Adams, Isaac Amanios, Bennetta Betbadal, Harry Bowman and Sierra Clayborn. Second row from left: Juan Espinoza, Aurora Godoy, Shannon Johnson, Larry Daniel Kaufman and Damian Meins. Bottom row from left: Tin Nguyen, Nicholas Thalasinos, Yvette Velasco and Michael Wetze

More than 48 hours  after the deadly shooting in San Bernardino of Southern California that killed 14 innocents and injured 21 on Wednesday, some  mysteries still shroud the tragic incident as further investigation was underway.

Authorities said the suspected shooter, 28-year-old U.S. citizen Syed  Rizwan Farook and his wife Tashfeen Malik, 27, had more than 1,600 rounds left when they were killed. At home, they had more than 4,500 rounds, as well as 12 pipe bombs and tools to make explosive devices.

It is not ordinary workplace violence, local analysts said, and their true motive remains elusive.

Farook had worked for the San Bernardino County Health Department for five years. On the day of the shooting, he attended the department’s holiday party at the conference room of the Inland Regional Center, but left early for unknown reason and returned with his wife, and weapons.

U.S. President Barack Obama said Thursday morning that there may be mixed motives in all of this, and FBI will go to get to the bottom of this.

Syed Rizwan Farook: one of the gunmen suspected to have links with IS

What the public concern most is that whether the shooting is terrorist-related.

David Bowdich, FBI regional assistant director, said at a news conference held in San Bernardino on Friday that the agency is investigating the shooting in San Bernardino as “an act of terrorism” based on the information and facts they have collected so far.

But he declined to confirm that it is a terrorist attack.

“The FBI defines terrorism very specifically. We cannot rule anything out at this point, we need to gather more evidence,” he said on previous occasions.

“That is the big question for us, is what is the motivation for this.”

James Comey, the FBI director, also said at a press conference Friday in Washington, D.C, that there is no evidence that the couple related to any terrorism network so far.

He said a man appearing of the Middle East origin asked a security guard of a local movie theatre about movie times, and theater hours at about 1 a.m. midnight, and another man later took some pictures of the theater.

Meanwhile, it remained unclear what is the couple’s true targets.

Because the couple had accumulated so many ammunitions and tools to make bombs, Bernardino Police Chief Jarrod Burguan said, they could be in some degree of planning to attack.

Analysts speculated that the couple’s true targets may not be the party given that most of their ammunition is left home.

At a press conference on Friday, Burguan described an incident that happened several days before the massing shooting.

He said a man appearing of the Middle East origin asked a security guard of a local movie theatre about movie times, and theater hours at about 1 a.m. midnight, and another man later took some pictures of the theater.

At the moment, no picture of Malik has been revealed to the public yet. It even triggered speculations that her name is not real as the authority is cautious to release all the information about her identity.

Attorney David Chelsey, who represents the family of the suspects, told media that investigators are “clueless” about Farook’s motivation. “There was nothing to characterize to make him act in this manner,” Chelsey said. He even doubted whether 90-pound Malik participated the shooting and carried the heavy ammunition and tactical gear.

“It just doesn’t make sense for these two to act like some kind of Bonnie and Clyde or something,” Chelsey told a media, “It’s just ridiculous.”

But Burguan confirmed with local media that during the gunfire which led to the deceases of Farook and Malik, there were two shooters firing from their car to police officers.

And according to Burguan, Malik was the same with her husband wearing black assault-style clothes when both were killed.

Bowdich said that they found two broken cellphones at the trash bin in the suspects’ home. “They are trying to destroy their digital finger prints,” he said.

He said more evidence may be found during further investigation.

*Reported by Xinhua