The extent to which AMC has grown as a home of original programming was seen at the TV Critics Association summer press tour Thursday when an executive session with the program chief was as intense as any with HBO.

Chief among concerns was the finale of “The Killing,” which some critics took personally as an affront that it did not identify a killer in the season-long case. While Joel Stillerman didn’t explicitly apologize, his tone suggested some wrong had indeed been done (when actually it had not,  of course, it was just a bigger twist than many saw coming or could accept, poor babies). A second season is on the way and the killer of Rosie Larson will definitively be spelled out, Stillerman promised.

Because “The Killing,” based on a hit Danish series, is character-driven, he says, he envisions a third season and further based on other crimes.

A bigger issue may have been the departure of Frank Darabont as show runner of “The Walking Dead” just before season two, but there were fewer questions about it. Stillerman wished him good luck, didn’t hint at reasons for the departure.

Glenn Mazzara will be show runner of “The Walking Dead,” which Stillerman says will hew close to the comic book source with having some surprising departures.

Of other AMC properties, production begins Aug. 8 on season five of “Mad Men,” to which they are committed up to season six.

“Breaking Bad” debuted this season with a 20 percent bump in the demo, but still there is no commitment to a fifth season.

The show AMC presented was “Hell on Wheels,” a sepia-toned new series depicting the building of the Transcontinental Railroad just after the Civil War, with Anson Mount, Common, Colm Meany, from John Shiban (“X-Files,” “Breaking Bad”) and Tony Gayton (“Faster,’ “Murder by Numbers”), starting Nov. 6.