I can't quite figure out which side of the issue would be making the threats. They also seem to be trying to drag Telegram into this, without clear evidence. The article doesn't say what type of books, but LGBT books were discussed at the Senate hearing mentioned below.

Link:
https://www.fox32chicago.com/news/chicago-area-libraries-bomb-threats

EXCERPTS:
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CHICAGO - Several libraries in the Chicago area, including Addison, Aurora, and Evanston, were targeted by bomb threats Tuesday.

The threats, which were later determined to be false, came as lawmakers went head-to-head on Capitol Hill over book bans in schools and libraries. Illinois Secretary of State Alexi Giannoulias testified in the U.S. Senate during the hearing.

Here at home, the threats led to evacuations and police responses across the city and suburbs. Some of the threats were sent to local libraries by email, while other branches received the startling messages through online chats.

Inside Chicago's largest library, an employee alerted police to a disturbing message. Officials say an anonymous email stated that a bomb was located somewhere inside the Harold Washington Library. The Bomb Squad and K9s searched the premises, but nothing was found.

A spokesperson for Chicago Public Libraries was not able to comment on the incident, as it is now a police investigation.

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"When these hoaxes come in like this, we call it a terrorist threat or causing a catastrophe," said Det. Rich Wistocki of BeSure Consulting. "You have kids who think it’s funny, they’re actually selling their services on Telegram, there are people paying them $50 for every shot."

Police have not released information on who was behind Tuesday’s library bomb threats, but according to FOX 32 Chicago’s cybersecurity experts, most ‘swatting’ or prank calls and messages are routed through a VPN.

"Virtual private networks, and when they’re using VPNs they think they can’t get caught but they can," said Wistocki.

Retired Naperville police detective and president of BeSure Consulting said oftentimes threats are sent from within the U.S., but through a foreign VPN – and that can make it more difficult to trace.

For example, Telegram – a cloud-based instant messaging service – which Wistocki said has been used in recent, local swatting incidents, is based out of the United Arab Emirates.

"And we can’t trace that because they’re not cooperating with law enforcement investigations," said Wistocki.

Wistocki said offenders could face between 10 and 30 years in prison, if convicted.

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