The agency said Tuesday that it processed 185,345 background checks roughly two per second on the same day that three people were killed and nine others wounded in an attack at a Planned Parenthood office in the state of Colorado.
The group provides health services to women, including abortions.
The FBI received about 5 per cent fewer background check requests on Black Friday in 2014, the agency said. FBI background checks processed by the National Instant Criminal Background Check System are conducted for gun purchases from federally licensed deals and for permits to carry guns.
The FBI started processing background checks for potential gun owners in 1998 as part of the Brady Handgun Violence Prevention Act.
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The previous record for the most background checks in a single day was December 21, 2012, about a week after 20 children and six adults were shot to death in a Connecticut elementary school. The week following the shootings at Sandy Hook Elementary School saw the processing of 953,613 gun background checks.
After the Colorado shootings, President Barack Obama again called for stricter limits on the availability of guns. "Enough is enough," Obama said in a statement Saturday.
Robert Lewis Dear, 57, is accused of killing a local police officer and two others in the shooting rampage. He is expected to be formally charged later this month.
Law enforcement officials have not disclosed details about multiple weapons found after Dear's arrest.