SPOILER WARNING: This article contains spoilers for The Flash #57, by Joshua Williamson, Scott Kolins, Luis Guerrero and Steve Wands, and is on sale now.
For the Flashes, the DC Universe is an awfully dangerous place, and it's even more treacherous these days. Wally West has seemingly perished at the beginning of the ongoing crossover Heroes in Crisis, and now, another one of the Flashes in DC's Multiverse has also been murdered in a (presumably) unrelated incident.
With Barry Allen busy trying to save the villain Heat Wave's brain, the time-traveling villain Hunter Zolomon killed Johnny Thunder, the cowboy Flash of Earth-18 in The Flash #57.
Now calling himself The True Flash (we'll see if that full name sticks, but given Zolomon's ego...) and wearing a version of the classic Flash costume, Zolomon has been on the warpath since he reemerged in the lead-up to the recent "Flash War" crossover. In that storyline, the villain formerly known as Zoom and the third Reverse-Flash broke the Speed Force that fuels the Flash's super-speed, in the process unlocking the power of the Strength Force and the mind-enhancing Sage Force.
When Barry Allen was trying to understand the relationship between the Speed Force and these new forces, he met with the Flashes from other alternate realities at the House of Heroes, essentially a clubhouse for heroes all across the DC Multiverse. In The Flash #52, Johnny Thunder and a few other Flashes urged Barry to go on a Force Quest to get a deeper, more spiritual understanding of the Speed Force.
Having gotten wind of the Flashes' get-together, Zolomon travels to Thunder's homeworld and sucks the life out of the speedster after a quick, brutal interrogation in The Flash #57.
Johnny Thunder was the Flash on Earth-18, a world filled with Wild West versions of Superman, Wonder Woman and various other cowboy-themed superheroes. This western world is largely inspired by Justice Riders, a 1997 Elseworlds one-shot by Chuck Dixon and J. H. Williams III. Set on Earth-1890, Wallace West, aka Kid Flash, was a super-speedy gunslinger with the quickest draw in the West.
After Infinite Crisis established Earth-18 as one of DC's 52 parallel worlds, Thunder took over as the western world's resident Flash. While DC's history has a few other heroes and western characters named Johnny Thunder, this Western speedster adopted Kid Flash's six-shooters as well as his role in the Justice Riders, the Wild West world's version of the Justice League.
While Thunder and Earth-18 have only ever appeared in passing, The Multiversity Guidebook filled out some of the world's history. In this reality, the Time Trapper, a time-traveling Legion of Super-Heroes villain, froze this world's culture and technology in the 19th century. This led to steampunk-influenced innovations like the Westworld-style mechanical horses that Thunder and his teammates rode.
Despite his lightning-quick reflexes, Thunder wasn't fast enough to stop Zolomon, who dismantled the famed revolvers right in front of the hero's shocked face. Right now, it's unclear whether Zolomon will go on a Spider-Verse-like quest to hunt down other alternate reality Flashes, but that would certainly make sense as part of the villain's plan. Regardless of what move he makes next, Zolomon still has his sights set on finishing the job he started in "Flash War" and taking out Barry Allen. But even if Barry finds a way to defeat Zolomon, Johnny Thunder won't be riding alongside the Flash off into the sunset.