Opponents of social media say that it bridges physical distance to build communities of like-minded people.

But what binds them together can sometimes be hatred and violence.

The joint investigation by ProPublica and PBS Frontline details the shadowy world of online hate networks.

Their investigation focuses on the platform, Telegram, and it's detailed in a new documentary,

the rise and fall of Terrorgram.

At first, it's just a handful of chat rooms and channels on Telegram.

Then it is bigger and bigger and bigger, and finally, it takes on a formal shape.

And people within that group say, now we're starting something called the Teragram

collective.

And this is going to be our organized arm that is going to generate in-depth propaganda,

in-depth material for this community.

The investigation identified 35 crimes linked to

Terragram, including bomb plots, stabbing, and shootings.

A.C. Thompson, who just saw there,

is one of the reporters who worked on the project.

He covers hate crimes and racial extremism for ProPublica and PBS Frontline.

AC, for people who aren't familiar with Telegram, what is it about this platform that makes

it so attractive to the people who form Teragram?

Telegram is a massive, massive platform. About a billion people use it most of them outside

of the U.S.

What was appealing to various types of extremists about Telegram was the fact that there was

very little moderation on it. So for a very long time, extremists of all different types,

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