The article was about a child porn raid that killed two of its agents - the suspect committed suicide afterwards 

The raid was at 6am and USA Today published at 9.30am 

The subpoena asks for the IP addresses and phone numbers of everyone  who clicked on the story between 8.03pm and 8.38pm that night 

The FBI Agent who issued it - J. Brooke Donahue - doesn't say why he wants that specific information, just that it will aide an ongoing investigation 

USA Today's owner, Gannett, is pushing back, calling the subpoena a violation of the First Amendment