Minneapolis school shooting: New video shows Annunciation School shooter at gun shop days before attack

New video footage shows the suspect in last week's mass shooting at a Minneapolis Catholic school buying a firearm at a gun shop just days before the attack.

The video footage, obtained by ABC Minneapolis affiliate KSTP , shows 23-year-old Robin Westman inside Frontiersman Sports for about 40 minutes on Aug. 23 -- just days before the shooting attack at the Annunciation School -- buying a .38 special revolver, according to the station.

That gun was not one of the three that police have said were used in the shooting rampage, according to the store owner, KSTP reported.

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In the new video, Westman, with hair pulled back in a ponytail and wearing a T-shirt, is seen browsing the firearms and, at one point, even hoisting a rifle and aiming it.

The gun shop owner, Kory Krause, told KSTP he has turned over the surveillance video to federal authorities who are investigating the shooting and said he's also sharing it publicly to try to shed light on the shooter's behavior in the days before the attack, which Krause said did not exhibit any of the red flags his staff are trained to look for.

He said Westman was friendly and "jovial" and smiled, laughed and asked questions, interacting with staff members.

Police said Westman is believed to have used three guns in the attack -- a rifle, a shotgun and a handgun -- firing through the church's windows as young students had gathered for morning mass.

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Two children -- 8-year-old Fletcher Merkel and 10-year-old Harper Moyski -- were killed, and 21 other people, nearly all children also, were wounded. Westman later died from a self-inflicted gunshot wound, according to police.

Police have said all of the guns used in the attack were purchased legally and recently by Westman.

A motive in the shooting remains under investigation, but authorities have said Westman, who left behind writings and videos, expressed hate toward many groups and had an obsession with previous mass shooters.