Bowdich described the 18-minute gap as critical because authorities do not know if the two attackers — Siyed Rizwan Farook and Tashfeen Malik, who killed 14 people at a company holiday gathering — went to a home, business or made any contact with anyone else, he said.

“Until we close that gap we just don’t know for sure,” he said.

The four-hour period between the attack and the gun battle had been a mystery in the weeks since the fatal attack. Authorities had not released many details about what Farook and Malik did before police officers found their vehicle, chased them and, ultimately, killed them in a shootout involving hundreds of gunshots fired on a residential street.

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On the morning of Dec. 2, Farook traveled to the Inland Regional Center for a company event. He was there for nearly two hours before he left for 19 minutes, then returned with his wife, which is when the shooting took place, Bowdich said.

What happened next is still not fully clear. Bowdich said that traffic cameras, surveillance footage, witness accounts and other resources helped investigators figure out some of the places Farook and Malik drove and spent time, though they do not necessarily know everything the couple did when they stopped.

About 45 minutes after the shooting, the pair went to Lake Seccombe in the city, Bowdich said, so evidence recovery divers were sent into the water to see what they could find. On Tuesday, Bowdich said that items were recovered from that lake, but none appeared relevant to the investigation.

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An hour after that stop, though, is a window that remains mysterious to officials. Between 12:59 p.m. and 1:17 p.m., “we’re dark,” Bowdich said Tuesday.

Bowdich also reiterated that authorities do not believe the shooters were directed by any outside organization.

“As of today, we do not see any indications of a foreign-directed terrorist act,” he said. “This seems to be an inspired terrorist act.”

Farook and Malik had discussed “their joint commitment to jihad and to martyrdom” in private messages exchanged online, discussions that occurred as long as two years before the attack, FBI Director James B. Comey said last month.

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Shortly after the shooting, Malik posted a note on Facebook pledging her allegiance to Abu Bakr al-Baghdadi, the emir of the self-proclaimed Islamic State. Authorities say this posting was also made on behalf of her husband. The Islamic State later said that two “supporters” had carried out the attack, praising the shooting without directly claiming responsibility for it.

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Last month, police arrested a former neighbor of Malik’s who bought the assault rifles that were later used in the San Bernardino shooting. Enrique Marquez Jr. was charged with conspiring to carry out other terrorist attacks with Malik in 2012.

Federal officials alleged that Marquez and Malik had planned to attack other targets, including a community college and a highway.

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