Oxygen audiences are no strangers to some of the deadliest serial killers in the nation. Jeffrey Dahmer , for example, earned notoriety for the cannibalistic murders of 17 young men and boys in the Milwaukee area. John Wayne Gacy , too, became infamous for brutally murdering dozens of victims and hiding their bodies in his crawlspace. Ted Bundy killed a string of women in the mid-70s, though his exact body count remains unknown. Unknown Serial Killers of America , a new Oxygen original series premiering Sunday, May 18, 2025, takes a look at the lesser-known serial killers of the country, some of whom were perhaps even more prolific than their more infamous counterparts. Each of the six episodes puts a name to the likes of The Sunday Morning Slasher and The Chameleon Killer, plus more. And while many uncaptured killers, including Jack the Ripper and the Zodiac Killer , are well-known to even the most seasoned Oxygen viewers, here are a few not-as-famous American cases in which the killer (or killers) has never been identified.
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