Take a look at this screenshot from a surveillance video.

At first glance, there's nothing immediately off about it.

The scene looks calm, almost routine.

But take a closer look or let the video play just a little bit longer, and this becomes

one of the most disturbing and confusing pieces of surveillance footage ever captured.

As always, view discretion is strongly advised.

The morning of April 18, 2016 was thunderstorming over Midlothian Texas and while most people were still

in bed, a woman named Terry, also known as Missy, was already awake and getting ready.

At 45 years old, Missy had a full plate and wore a lot of hats.

She was a wife, a mother to three daughters, a former special education teacher and now

a fitness instructor.

In the city where she lived with her husband and their girls, Missy had become a fixture in the local fitness scene. Her early morning boot camps during locals looking to get in a workout before work, and the group had become a bunch of regulars who enjoyed the motivation and consistency they each brought to the group. Usually, these classes took place outside in the parking lot of a church, but with the forecast the night before, Missy had sent a message to the group, letting them know they would be moving indoors.

Somewhere around 4 a.m. that morning, Missy loaded her workout gear into her vehicle and drove through the rain towards the church.

What she didn't know, however, was that someone was already inside.

By the time she arrived, it was getting close to

4.15 and the church was dark and quiet except for the storm outside. She then parked,

grabbed her gear and headed inside to set up for her 5 a.m. class. As was captured by the church's

surveillance cameras, her movements were routine and completely unremarkable. This footage would later

become some of the most disturbing in recent

true crime history. At exactly 4.18 a.m., Missy was seen entering the building on camera, walking

alone through the hallways. It was fairly clear at this point that she had no idea someone else

was already there. The next recorded moment came close to 4.35am when one of Missy's students arrived for class.

...