I take Maloy as a dubious source as he was a newspaper competitor and political foe of Baker. And in at least one place he claims that fifth person was Quantrill himself.

O'Dell claims William Reed in this paper: pg. 48 https://archive.org/details/fl-2194038-tn-2221116/page/48/mode/2up?q=reed

I also ran across it relating to AI Baker's arrest but I well need to dig in my history a bit. May have been Van Natta.