The suspected shooter in the Orlando, Fla., nightclub attack legally purchased firearms, an official from the Bureau of Alcohol, Tobacco, Firearms and Explosives confirmed Sunday afternoon.

Trevor Velinor, assistant special agent in charge at ATF, said the agency had traced the firearms used and confirmed that the suspect could legally walk into a gun dealership and "acquire and purchase firearms."

BREAKING: ATF Orlando "We have completed urgent traces on firearms involved in #Orlando shooting. Firearms purchased legally." — ATF HQ (@ATFHQ) June 12, 2016

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The suspect, Omar Mateen, purchased at least two firearms "within the last week or so," he said.

The official declined to give the location of the purchase because of the ongoing investigation.

The attack at a gay nightclub in Orlando, which occurred during Pride Month, left 50 dead and many more wounded, making it the worst mass-shooting incident in U.S. history.

The suspect had been interviewed by the FBI three times before the shooting at the Orlando nightclub, the agency announced Sunday.

He had called 911 before the shooting and pledged his allegiance to the Islamic State in Iraq and Syria.