There will be some spoilers for RED LANTERNS #21, still on sale.
Charles Soule has recently taken over RED LANTERNS and issue #21 was pretty intense. With Guy Gardner meant to go undercover to keep tabs on the Red Lantern Corps for Hal Jordan, the encounter between Guy and Atrocitus may not have gone according to plan.
We saw Atrocitus defeated and Dex-Starr took him away. What many of us may have forgotten is the fact that the Red Power Ring replaces the Red Lanterns' hearts. It was in our interview with Charles Soule at San Diego Comic-Con where this was brought to our attention (at 3:10).
"He has been killed to death." This makes sense. We saw it happen in the beginning of the issue with Phist. I think we just all assumed Soule wouldn't kill off Atrocitus in his first issue. Looks like we were wrong. But it is a "comic book death" so we'll have to see what's next.
If you haven't checked out RED LANTERNS #21, you'll want to track down a copy. Issue #22 is on sale July 31.