San Bernardino police said late Wednesday they were “reasonably confident” the two suspects shot dead during a gunfight in Redlands, Calif., were the same two shooters who killed 14 and injured 17 at the nearby Inland Regional Center earlier that day and that there was no third person involved. While unable to determine a motive so far, police also said they have not ruled out terrorism.

It is extremely rare for a mass shooting in America to have multiple perpetrators – and even more so for one of them to be a woman.

At a press conference Wednesday night, San Bernardino Police Chief Jarrod Burguan identified the suspects killed in the shootout with police as Syed Rizwan Farook, 28, and Tashfeen Malik, 27.

Burguan said they were either married or engaged, and later said in response to a question that they could have been boyfriend and girlfriend.

Hussam Ayloush, executive director of the Council for American-Islamic Relations in Los Angeles, told The Washington Post that Farook and Malik had been married for two years and left their 6-month-old child with Farook’s mother that morning.

The couple told the grandmother that they had a doctor’s appointment and needed her to take care of the child, Ayloush said, adding that she had been concerned Farook and his wife might be among the victims when neither of them answered their phones.

“I have no idea why he would do something like this,” Farhan Khan, who is married to Farook’s sister, said at a news conference held by CAIR-LA late Wednesday night.

The police chief said while they are still searching for a motive, “We have not ruled out terrorism.”

Farook was a San Bernardino County employee who had worked for five years as an environmental health specialist in the public health department, which was hosting the holiday party where the shooting occurred Wednesday. According to state employee records, Farook’s total compensation in 2013, including salary and benefits, was $71,230.

He was born in the United States, Burguan confirmed, though Malik’s origins are still unknown.

Farook was born in Illinois after his parents immigrated to the U.S. from Pakistan, Ayloush told The Washington Post. He said Malik was born in Pakistan and lived in Saudi Arabia before the marriage.

The California couple join a long roster of convicted and alleged mass shooters from recent years. But in contrast to those who have committed such acts of violence in the past, Farook and Malik do not appear so far to have left a digital trail that could point to their motives.

Christopher Harper-Mercer, the 26-year-old who fatally shot nine people and then killed himself at a community college in Oregon in October, left behind social media profiles that indicated an affinity with Nazism, anti-religious views and a desire to “lash out at society.”

Charleston, S.C., church shooting suspect Dylann Roof posted Facebook photos of himself wearing emblems of white supremacist movements, and owned a website containing a lengthy manifesto against racial minorities.

But where Farook and Malik are concerned, what traces of them can be found on the Internet are benign: a baby registry that appeared to be in Malik’s name, and an undated online dating profile that appeared to be Farook’s, in which, among other things, he stated an interest in target shooting.

The registry page cites a May due date in Riverside, which corresponds with reports that the couple’s child is 6 months old and the fact that they were discovered by police outside a residence less than half an hour away from Riverside.

Malik’s requests are few: diapers, baby wash, swabs and convertible car seat.

The dating profile, posted to a site “for people with disabilities and second marriage,” includes a description that matches what is known of Farook so far.

The profile’s “About Him” section introduces someone who works for the county as a “health, safety and envorimental [sic] inspector.” It further states that he is from a religious but modern family of four, lives with his parents and enjoys working on cars as well as “just hang out in back yard doing target pratice [sic] with younger sister and friends.”

In interviews with the Los Angeles Times, Farook’s co-workers in the public health department said he was “quiet and polite, with no obvious grudges.”

“He never struck me as a fanatic, he never struck me as suspicious,” Griselda Reisinger said.

Fellow inspectors Patrick Baccari and Christian Nwadike said the “tall, thin young man with a full beard,” rarely started conversations, but he was well-liked and spent a lot of time out in the field.

They said Farook recently traveled to Saudi Arabia, coming back with a wife he had met online. He was a devout Muslim, but didn’t discuss religion at work.

Reports show that Farook inspected public pools and eating establishments. His job required him to check the cleanliness of food surfaces and cooling methods, analyze chlorine levels and test kitchen equipment.

Police Chief Burguan said Farook was at Wednesday’s holiday party but left “under circumstances described as angry or something of that nature.” Nevertheless, signs pointed to the attack being premeditated: the shooters were wearing tactical gear, black masks and carrying multiple weapons.

“They came prepared to do what they did as if they were on a mission,” Burguan said. “Based upon what we have seen and how they were equipped, there had to be some degree of planning that went into this. I don’t think they grabbed the guns and tactical gear on a spur-of-the-moment thing.”