Hey there, Shankar here. The Hidden Brain team has been transfixed by the nationwide protests in recent weeks.

The enormous number of demonstrators may be new, but the biases they're protesting are not.

In 2017, we produced an episode on a little-known form of racial bias.

We decided to return to that episode now as many people are pushing for reforms in the criminal justice system.

Please note that the episode includes the sounds of shootings from a college campus, as well as music with violent and explicit language.

Here's the episode.

On a chilly April morning in 2007, a nightmare unfolded on a college campus in Virginia, a 23-year-old student acting alone, open fire in a dormitory.

He shot and killed two students.

Then he walked across campus and began killing people in an engineering building. The sound of gunfire was caught on a student's cell phone.

We weren't sure what it was. It was gunshots, but for while we thought it would have been construction, we heard this horrible scream and laughter.

Tina Harrison was a student in the building.

We were sitting in the classroom and basically panicked for a go. All we could hear was people screaming, laughter, and more screaming.

I counted 24 gunshots within a minute, and I lost track after that. I just started praying.

By the time the assault ended, 32 people were dead. The gunman took his own life.

The shooting at Virginia Tech was quickly seared into our minds as one of the deadliest mass shootings in US history. Unfortunately, it's been followed by many other school shootings, including the killing of 17 students in Parkland, Florida.

In all these cases, the news media has struggled to convey the sheer scale of the massacre.

There is terror and then sorrow today at the campus of Virginia Tech.

An act of evil on a scale that we've never seen in this country before. For hours. After the news began to break, Blacksburg, Virginia is still in shock from its wounds.

But even as the country mourned, people began to ask why campus officials hadn't been more proactive.

Why hadn't they spotted the warning signs? Why hadn't they locked down the school after the first shooting of the dorm? At a press conference, campus police tried to explain.

We had information from witnesses and the evidence at the scene that led us to believe the shooter was no longer in the building and more likely off campus.

The reporter's grilled officials, who at times seemed lost for words.

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