AMNA NAWAZ: As investigators continue to seek answers about what drove the young man accused of killing conservative activist Charlie Kirk, conspiracies about who he is and what he believed are flourishing.

William Brangham takes a closer look at what we know about the suspect's life online.

WILLIAM BRANGHAM: One focal point for investigators are the inscriptions carved onto the bullet casings that were believed to be owned by the alleged shooter.

They contain a number of seemingly sarcastic, irreverent phrases that are common in gaming and online communities, phrases like "Bella Ciao" and "Hey, fascist, catch," and a series of arrows, up, right, and several pointing down.

So to help us decipher what those inscriptions might mean, we turn to Ryan Broderick.

He's the author of the newsletter called Garbage Day and host of the podcast "Panic World."

Ryan Broderick, thank you so much for being here.

We heard earlier today the latest on the investigation into this alleged shooter, but I want to ask you about those bullet casings.

They clearly imply that the suspect lived a very, very online, Internet-focused life, heavily steeped in gaming and these subcultures.

From your expertise, what can we glean by what was written on those bullet casings?

RYAN BRODERICK, Host, "Panic World": Well, the bullet that struck and killed Charlie Kirk allegedly had a phrase of a very common meme written on it.

It is part of a subculture called furries.

They are people who dress up in animal costumes.

And this screenshot has been traveling around the Internet forever.

It doesn't mean that Robinson is a member of that subculture, but he is of an age where he would have grown up online seeing it everywhere.

It's a bit of what they would call cringe humor.

The other bullets recovered by law enforcement include a reference to the satirical, the fascist video game "Helldivers 2."

You basically play as fascists in space.

And the message "Hey, fascist, catch" with the arrows written on it references the most powerful bomb attack in the game.

So the idea was, you play those buttons, you throw the bomb, it's a massive explosion.

The other bullet referenced by law enforcement is the Italian folk song "Bella Ciao."

It is common among anti-fascist and leftist communities, but it's also a popular fixture in pop culture.

It was used in Netflix's show "Money Heist."

It's referenced in the video game "Far Cry 6."

And then the last one, which reads "You're gay LMAO," is what you would just call boilerplate troll behavior.

It's meant to embarrass any sort of law enforcement investigator looking at the bullets.

How dare you try to find meaning in what I have written on these bullets, which is something that we have seen with a lot of other young Gen Z extremists over the last year or two.

WILLIAM BRANGHAM: So should we take these comments literally?

Are they meant to be tongue-in-cheek, jokey?

Are they some combination?

I mean, it sounds like it's very hard to glean an ideology here.

RYAN BRODERICK: That is that is the main question.

So it is possible that Robinson is a leftist, an anti-fascist, someone you would consider on the political left.

It's equally possible that he is trying to muddy the waters.

And we have seen this with other spree shooters at schools across the country this year, where a shooter will write conflicting political messages.

In Nashville, Minneapolis, we have seen this.

Dating all the way back to 2019, with the use of memes in the Christchurch shooting in New Zealand, this is a common tactic for what you would call an accelerationist.

For those who aren't familiar, an accelerationist is someone who wants to accelerate the end of the status quo, end of society, someone who wants to push politics and political violence to such an extreme that the order of the country would fall apart.

It is a very nihilistic, very apocalyptic view that has become more and more popular, particularly on the dark corners of the Internet in the last 10 years.

WILLIAM BRANGHAM: So, when the -- when Utah's Republican Governor Spencer Cox says that this is evidence of leftist ideology, you seem to believe that's not nearly as clear-cut with what we know now?

RYAN BRODERICK: I don't think so, but we have seen these tactics used on the far right more commonly.

They know the playbook after an incident like this.

So, with law enforcement digging through manifestos, looking for evidence of a larger ideology, this is a pattern we see after every incident like this, and young extremists know this.

WILLIAM BRANGHAM: So, clearly, as you're saying, this person lived a very, very steeped in the online world life.

How has Charlie Kirk's murder been viewed online, broadly speaking?

RYAN BRODERICK: Well, you have to imagine this is going exactly according to plan.

Charlie Kirk's death was telegraphed for social media.

It took place at a public event where Kirk was surrounded by smartphones.

The shooter would have known that there would be an audience.

Charlie Kirk is an extremely popular influencer on the right and a very well-known figure of derision on the left.

He's a very -- he was a very polarizing figure, right?

And so the minute that footage of his death hit social media, it went more viral than I think anything we have ever seen like this.

And now the wild goose chase that Internet users are going on to figure out why Robinson allegedly carried out the attack fits perfectly in with previous shootings like this.

If you wanted to cause as much chaos online, this is exactly how you would do it.

And we have seen this with Internet users digging through Tyler Robinson's mother's Facebook history, looking for any sort of meaning in the memes written on the bullets themselves, and then the general chaos of the modern social media age.

So we have seen conspiracy theories.

We have seen A.I.

play a prominent role in misinformation.

It is complete chaos.

And that is only exacerbated by the way that the Trump administration and the FBI have been handling this in the public, putting out as much info as they can, even though it's conflicting, sending people off in different directions about what may have happened.

It is an information nightmare.

WILLIAM BRANGHAM: Amidst all this, we're seeing so much of an attempt to pin the blame on left-wing ideology or right-wing ideology.

Is that the right way to think about or talk about these online subcultures?

RYAN BRODERICK: I don't believe so.

I think the thing to really focus on here is that Tyler Robinson is of a generation that has grown up in America where there have always been school shootings, always been spree shootings.

And many young people, many young extremists that we have seen come out of the woodwork over the last few years since the pandemic see public violence as a path towards fame, towards glory, another way to go viral.

And they talk about this on platforms like Discord and Web sites like 4chan.

This is common knowledge for young people.

And so, of course, there is the knee-jerk reaction to blame this on anti-fascists or leftists or trans communities or right-wing commentators.

But this is a larger problem, a much more politically complex problem.

And it's one that is very ingrained in American society in the 21st century at this point.

WILLIAM BRANGHAM: All right, that is writer and podcaster Ryan Broderick.

Thank you so much for being here.

RYAN BRODERICK: Thanks for having me.