update: Found one of them,
https://news.ycombinator.com/item?id=1692754 ("Google fired engineer for breaking internal privacy policies" (2010))
It's not linked in there, but the Wired writeup adds that (0) there were at least two SRE's fired for something like this and (1) Google chose not to report this to law enforcement, seemingly prioritizing its public image over its users' safety.
https://www.wired.com/2010/09/google-spy/ ("Ex-Googler Allegedly Spied on User E-Mails, Chats" (2010))