It's hard to say just what the facts are with Porter Rockwell, so much sensationalism was built up around him. He was actually arrested for the attempt on Bogg's life, put in jail, but "allowed" to escape. They may have realized their "evidence" wasn't all that good. (Odd, that never seemed to bother them all the times they arrested Joseph Smith on trumped up charges).
The comment I heard Rockwell made was "...I'm just sorry I missed..."
A heavily researched biography of Rockwell has him in another jail on trumped up charges at the time of the assassination attempt, assuming the records are accurate.