A musician by the name of Robert N. Marley confessed at the time to the killing. He was adamant that he was not also responsible for the shooting of the deputy, and while this seems rather implausible at first glance, it would be curious indeed to confess to one shooting and not the other if there was not some truth in it.
Since the original confession however, the credence of Robert's initial confession has been brought into question by multiple others claiming to have carried out the deed. An Englishman by the name of Eric P. Clapton soon claimed to be the shooter, and much later a Californian, Warren Griffin III, tried to take credit. In his case though the sequence of events described differed markedly from the original narrative, leading less credence to his version of events.
I cannot hide the truth any longer. I have carried it far to long. My soul cries for absolution and forgiveness. I am willing to accept whatever punishment deemed just for my actions.
I saw the deputy get killed. The one who did it was Col. Mustard, in the conservatory, with the candlestick.
The Problem, as has been noted by many post-Apocalyptic Scholars, is that the Murder of Lucas Simms was immediately followed by the rather dramatic eradication of the crime scene, trace evidence, witnesses, and indeed surrounding countryside. As described in Allistair Tennpenny's seminal work on dramatic landscaping, The Powder and the Atom: Better Urban Renewal and Scenic Vistas through the Power of Fission, there is a suggestion the enigmatic figure known as "The Lone Wanderer" -- who may or may not have been a Vault Dweller -- was responsible for the death of Sheriff Simms. That being said, ghoul Roy Phelps hotly disputed this version of events in his hand-scrawled graffito found on the side of a burning bus, which has been termed by scholars as the "Tennpenny Trap Monument," BURKE DID IT. There have been rumours that a new work coming out of New vegas may clarify the situation.
While I confess to shooting the sherif, I have always maintained my innocence in relation to the death of the deputy.
To piggy back onto your question: I shot the clerk? I shot the clerk?