Investigators looking into a report that someone resembling one of the San Bernardino shooters tried to enter a downtown Los Angeles high-rise building in recent weeks determined that man was not 28-year-old Syed Rizwan Farook, who went on a rampage with his wife Wednesday that killed 14 and injured 21 at a holiday luncheon.
Building management said someone who looked like Farook and another man unsuccessfully tried to enter the 53-story tower at 601 Figueroa Street, sources told the NBC News Investigative Unit. Mayor Eric Garcetti confirmed that the city passed along information about the report to the FBI to determine whether there was any link to Wednesday's shooting.
The FBI said later Tuesday that the individual, described by a building security guard, was not Farook. The security guard had seen a photo of Farook after the San Bernardino shootings and thought he turned away from the building, according to the FBI.
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Garcetti said the report and follow-up investigation illustrate a heightened awareness of potential public safety threats following the attack.
"Don't be paralyzed, but be vigilant," said Mayor Eric Garcetti. "Be a part of this."
Law enforcement sources told NBC News they were investigating the report as part of a look at possible other plans by Farook and wife Tashfeen Malik. The couple were killed hours after the massacre in a gunbattle with police, which occurred around the same time Malik pledged allegiance to the Islamic State group on Facebook, authorities said.
Investigators are attempting to determine whether the attack was part of a broader plot, and if so, who might have financed it. NBC News has confirmed that the attackers received an unusual $28,500 deposit in the weeks before the shootings, but details regarding the source of the money were not immediately available.
On Monday, the FBI said Farook and Malik had been radicalized "for some time" and did target practice before the rampage. ISIS has not claimed responsibility for the San Bernardino massacre but said the assault was perpetrated by followers of the group.
The FBI is investigating the massacre as a terrorist attack that, if proved, would be the deadliest by Islamic extremists on American soil since Sept. 11, 2001. FBI Director James Comey has said there was no indication yet that the plot was directed by any other foreign terrorist group, though he would not rule out that future possibility.
NBC4's Jonathan Lloyd and Toni Guinyard contributed to this report.