The 17-year-old star - who is expecting her first child with Casey - was filmed driving along a dirt trail in an all-terrain vehicle in Kentwood, Louisiana, with 18-year-old Casey when he started shouting at a photographer who, he alleged, was trespassing on private property.
The video from gossip website tmz.com shows Casey brandishing what appears to be a gun or another form of weapon from his pocket when the photographer refuses to leave.
Casey and Jamie Lynn then drove off.
Jamie Lynn is reported to be expecting a baby girl after she was spotted loading a pink baby carrier into her vehicle.
Following reports Casey proposed to the 'Zoey 101' actress earlier this month, Jamie Lynn wore a T-shirt bearing the slogan 'The Rumours Are True' and showed off her diamond engagement ring.
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