Parents and children settled into their seats for a new animated Disney film got a quick jolt when a horror movie came on the southwest Ohio screen instead. The Hamilton-Middletown Journal-News reports that a projectionist accidentally played “Insidious: Chapter 3” instead of “Inside Out.” A mother wrote about the incident on the newspaper’s Facebook page, saying her children were scared and she and other adults scooped up their kids and left.

Parents and children settled into their seats for a new animated Disney film got a quick jolt when a horror movie came on the southwest Ohio screen instead. The Hamilton-Middletown Journal-News reports that a projectionist accidentally played “Insidious: Chapter 3” instead of “Inside Out.” A mother wrote about the incident on the newspaper’s Facebook page, saying her children were scared and she and other adults scooped up their kids and left.

This happens quite often. 
From someone I know who used to work in a theater, sometimes it’s done intentionally .. 

While I am not implying that was the case this time, it certainly seems to be quite a big accident..