As explained in a local NBC News report, the Dreadhead Cowboy—a.k.a. Adam Hollingsworth—pulled the stunt as part of an effort to amplify the "kids lives matter" message. In a Facebook post, Hollingsworth told fans that he will keep trying to shut down the Dan Ryan Expressway "until we understand that nothing else matters."
Critics of the highway display included those who were concerned for the safety and general wellbeing of the horse, with local police later stating that the horse was bleeding from one of its hooves. Chicago Mayor Lori Lightfoot, who previously enlisted Hollingsworth to help with 2020 Census awareness over the summer, said this latest ride was an example of trying to call attention "to issues of great importance" in a "very wrong way."
Hollingsworth was ultimately arrested by Illinois State Police for reckless conduct, disobeying a police officer, and criminal trespass to state-supported property. Another man, identified by police as Darron Luster, was charged with obstructing and resisting arrest after allegedly attempting to "gain control of the horse" while state police were trying to observe the horse's injuries.
As of Monday the horse was "temporarily" in the custody of Animal Care and Control officials. According to a press release, Hollingsworth had met with police earlier this month about a protest he had planned for the Dan Ryan Expressway.
At that point, at least according to police's comments, Hollingsworth was told he would "not be allowed" on the expressway due to the inherent danger of such a stunt.