In the book Tales from The Mos Eisley Cantina, the other two Rodians in the Cantina at the time of that scene were present to execute Greedo (for a clan rivalry). Solo shooting Greedo let them claim the bounty. Every story in that book centers around the scenes from the film that took place inside the cantina.

0 - https://www.amazon.com/Tales-Eisley-Cantina-Star-Wars/dp/055...