Autopsy reports found from 1929 Valentine's Day massacre
The attack, carried out by men dressed as city police officers, is widely believed to have been ordered by famed Prohibition-era gangster Al Capone.
The victims of the Feb. 14, 1929 massacre were five men who were known gangsters working for Capone rival George "Bugs" Moran, an optometrist who was friends with Moran's crew and a mechanic at the garage that served as Moran's headquarters.
Since there was no evidence of a struggle, it's believed that Moran's men thought it was a police raid.
Other documents also outline the difficulties investigators faced while attempting to solve the crime, including witnesses who were too afraid to testify, the limits of forensic science and photographers who were eager to document the event.