Now, I said this series was going to cover horror comics, yet here I am looking at a crime comic, one purportedly drawn from a real life case. Although this story appeared in Justice Comics, it could have easily been printed in Mystery Tales or Suspense.
A string of murders committed by a man wielding a hammer unnerve the city; police detective John Murray notes the killer only strikes on night when rain is falling and makes this information public, upsetting the public when another rainfall occurs; however, no hammer murders follow the rain. It's only while looking at his son's book on mythology that Murray realizes what's really going on:
Murray missed a vital piece of information about the killings: they occur on nights with thunder & lightning. The killer has modeled himself after the Norse god of thunder, Thor! On the next storm night, Murray manages to save a policeman from being the next victim!
These leads Murray to a barrel-making factory, where there just happens to be a red-bearded barrel maker called...Thorson! Murray waits for another storm to burst out before he makes his move; sure enough, Thorson is the man they're looking for; he believes Thor is his father!
Thorson is dead, bringing an end to the hammer murders. Murray is left to wonder whether the lightning strike was a coincidence or godly intervention.
Like most crime comics, "Hammer Horror" claims to be based on a real life case. I've tried to ascertain if this is true, but I haven't had any luck; supposedly, this is from the casebook of "John Murray" of the "Black Daisy" case. These seem to be references to famed serial killer-catcher John St. John and the Black Dahlia case, but I haven't found any internet sources connecting St. John to this case; if you can identify the real world case, please let me know.
On the other hand, there's an old-time radio program which follows this same story! It's the October 11, 1949 episode of Casey, Crime Photographer dubbed "Thunderbolt." Just like "Hammer Horror," a man named Thorson kills men with a hammer on stormy evenings. This suggests that either the 1949 radio play and 1951 comic script both drew from the same historical sources, or the comic swiped the radio story and tried to pass it off as a "real case" to conceal the matter (50s comics are full of swipes from radio and short stories). Anyway, you can download "Thunderbolt" from the Internet Archive here (right-click to save the file); the surviving copy of this episode is missing the commercial and music bridges (being an AFRS broadcast), which makes it seem more intense than the typical episode of Casey. Also of interest, up until 1950 Atlas had been publishing a Casey, Crime Photographer comic book.