This undated photo provided by RR Auction shows part of a manuscript penned by Jack Ruby, who shot and killed Lee Harvey Oswald days after the assassination of President John F. Kennedy. The manuscript is up for auction Wednesday, Nov. 8, 2017. A medallion worn by Kennedy at Harvard University is also up for auction. (Photo: Cameron Johnson/RR Auction via AP)

Jack Ruby shocked the nation on Nov. 24, 1963 when, with reporters’ cameras broadcasting live, he shot and killed Lee Harvey Oswald just two days after Oswald assassinated President John F. Kennedy.

Now, over half a century later, a manuscript written by Ruby while in prison and awaiting the death penalty after being convicted of Oswald’s murder is up for auction.

The 24-page, handwritten manuscript details Ruby’s actions on the night of Kennedy’s assassination and early the next morning, and, according to Earl Ruby, the killer’s brother who signed an affidavit of authenticity in 1992, was intended to be used to prove that Oswald’s murder was not premeditated should Ruby receive a new trial.

RR Auction, the Boston-based auction house that will auction the manuscript off tonight at 7 p.m. ET, says the 22 sheets of 4 x 6 paper, etched by Ruby in pencil, are in “fine condition” and have an estimated worth of over $12,000.  

An excerpt from the manuscript describes Ruby—a nightclub owner from Dallas, Texas where Kennedy was shot—ordering sandwiches for detectives and radio reporters before going to the police station where he saw “this fellow”—Oswald—being escorted by police and surrounded by the press.

“(…) somehow I got caught into the swirl of things, and was standing in the long hallway when a door opened and they brought this fellow out, and I was very close to him,” Ruby wrote. “(…) I wasn’t too anxious to leave, because this was making history and I was a part of it.”

The next day, Ruby would return to the Dallas police station, again see Oswald being escorted by police, and shoot him once in the abdomen with a .38 revolver, assassinating the assassin.

Ruby’s written narrative corresponds with his testimony to the Warren Commission on June 7, 1964, according to the auction house.

Convicted of murder with malice and sentenced to death on March 14, 1964, Ruby later had his conviction overturned by the Texas Court of Criminal Appeals but died of a pulmonary embolism in custody before his second trial.

The auctioning of his manuscript comes shortly after the National Archives release of thousands of files related to the JFK assassination that were never before available to the public.

A medallion Kennedy wore at Harvard University is also up for auction today, according to the Associated Press.