Samuel Johnson was arrested in KC in November 2011: http://fox4kc.com/2011/11/10/burglary-alarm-leads-cops-to-drugs-ammo/
It would appear it was this arrest that led to the possession, intent to sell and the ammo charges. I guess news doesn't travel that well because, despite Johnson's November arrest being on TV in KC, he apparently turned informant, leading to the arrest of Coolley and 7 others from Columbia in Omaha the day of the NCAAT game in March 2012.
Reading between some lines here, it doesn't appear to me that authorities ever documented Coolley making a deal or that he was ever found in possession -- his name or voice likely turned up on wire-taps in connection with the people selling in Columbia.
Just as a point of order, "conspiracy to sell" charges are incredibly broad - per this commentary from a legal defense site:
"Federal agents are particularly interested in cases where they can charge multiple people of being involved in a conspiracy to sell or distribute cocaine. The essence of a conspiracy is an agreement to commit an illegal act. The most important aspect of conspiracy law is that everyone who is found to have been part of the conspiracy can be found guilty of committing any crime committed by any member of the conspiracy.
Under 18 USC § 846, the conspiracy law for drug trafficking cases, you can be found guilty of selling or possessing cocaine even if you personally never touched or sold any cocaine. If you conspired to sell cocaine but someone else in the conspiracy did, that can be enough to make you guilty of conspiracy to sell or distribute cocaine. In addition, you can be found to be part of a conspiracy with people you have never met or even spoken to. This is particularly likely to happen in large-scale federal cocaine conspiracy cases where prosecutors can charge ten or more people of being part of the same conspiracy."