Kyrie O’Connor, senior editor of the Houston Chronicle, a sister paper of the Hearst-owned Express-News, will join the Express-News today as interim editor. After graduating with a journalism degree from the University of Texas at Austin in 1999, the Edinburg native joined the Washington Post as a staff writer covering criminal justice issues.

Brett Thacker, a longtime veteran at the Express-News who started as a sports copy editor and rose through the ranks to become the No. 2 editor at the newspaper, sent an email to the newsroom Wednesday evening, bidding his colleagues farewell.

A short post late Tuesday set the Twitter feeds aflutter — longtime San Antonio Express-News editor Bob Rivard had resigned, shocking staffers at the daily’s afternoon newsroom meeting. The exact details of Rivard’s exit are still unclear (how much can you confidently glean from Twitter?), but by all accounts the announcement by Express-News publisher Tom Stephenson, absent Rivard’s presence, to newsroom staff was unexpected.

The announcement was made by publisher Tom Stephenson and Mark Aldam, a Hearst corporate exec, at about 4:40 this afternoon and is effective immediately, according to newsroom tweets by E-N journo John Tedesco. We’ll have more on Newsmonger soon, but first: the letter.

The top two editors at the Express-News bolted in as many days. Tall, silver-haired, and chronically affable, Brett Thacker (No. 2) resigned from the daily Wednesday, a day after executive editor Robert Rivard (No. 1) called it quits. Both forwarded sunny emails to E-N reporters and editors indicating their abrupt departures had been voluntary; Rivard’s arrived Tuesday afternoon, Thacker’s Wednesday evening.