Apparently he was some kind of wannabe gangster rapper.
There's another post here on KiA2 linking to a NY Post article.
The “person of interest” arrested in the deadly mass shooting at a Fourth of July parade outside Chicago on Monday has been identified as a 22-year-old local amateur rapper with a history of disturbing online posts.
Robert “Bobby” Crimo III, who performs as “Awake the Rapper,” posted a video to his since-deleted YouTube page that included an image of a man with a long gun face down in an apparent pool of blood with a few police officers standing in front of him, according to screenshots posted to social media.
Apparently he was some kind of wannabe gangster rapper.
There's another post here on KiA2 linking to a NY Post article.