January 6, 2016 10:30 AM EST

Federal officials say they need the public’s help in identifying the San Bernardino shooters’ movements during a missing 18 minutes on the day of the attack.

The 18-minute time lapse between 12:59 p.m. and 1:17 p.m took place after Tashfeen Malik and Syed Farook opened fire at a holiday party for Farook’s county health department and before the pair died in a car chase with police on Dec. 2, Fox News reports.

Authorities said Farook first walked into the party at 8:47 a.m. and left at 10:37 a.m. after already planting a backpack full of explosives at the site. He returned with his wife roughly 19 minutes later and began shooting.

Read more: Gun Buyer in San Bernardino Attack Faces Arraignment

Federal officials do not suspect the shooting was a foreign-directed attack, nor does it seem to stem from a workplace dispute.

“This seems to be an inspired attack,” FBI assistant director in charge David Bowdich said at a press conference Tuesday.

Since the shooting, authorities say they haven’t been able to piece together all of the terrorists’ movements.

Bowdich said officials have conducted hundreds of interviews, collected more than 500 pieces of evidence and served 29 search warrants. Investigators say they’ve found most of the pair’s travels, but are still in the dark on 18 minutes of movement.

Bowdich urged anyone with information on Farook and Malik’s movements during the missing time to call 1-800-225-5324.

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Write to Lauren French at laurenfrench651@gmail.com.

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