Courtesy of DDW, "DEA: South Florida 'dark web' dealer sold deadly heroin from China" announced the arrest of 'Owlcity', an AlphaBay seller of fentanyl, alpha-PVP, MDMA, cocaine, Xanax. The article incorrectly gives the arrest reason and sounds totally bizarre (he sent them the post office address...?), but when I looked up the complaint the complaint reveals what actually happened - after several undercover buys had localized Owlcity to South Florida, they made another order and:
On February 26, 2016, DEA agents received information from the U.S. Postal Service (USPS) that the tracking status of the Priority Mail package that OWLCITY sent to complete the October 23, 2015 heroin order was queried online on the U.S. Postal Service website from an IP address assigned by AT&T to an a ccount associated with the Leslie Residence.
They began in-person surveillance of Leslie, watched him drive to the post office with additional orders & intercepted the packages, ISP monitoring of Tor activity, correlation of Owlcity inactivity with computer repair, and finally a raid 27 July 2016.
obvious opsec pro-tip: Don't use either TOR or your real IP (VPN dude!) to check tracking numbers. One's a red flag that the package might be interesting to LE; the other is a simple bust.