Samuel Little is being called the most prolific serial killer in U.S. history after authorities verified more than half of the 93 murders he's confessed to during a 35-year span.
The 79-year-old Texas inmate was already serving three consecutive life sentences when he confessed to another 90 killings last year, NBC News reported.
On Monday, the FBI confirmed that its investigators verified 50 of those deaths and are seeking help to confirm the rest of the unmatched confessions.
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This story has been corrected to report Little is currently an inmate in Texas