Chicago police are investigating to find out how 32-year-old Michael Arquero–“a convicted felon and documented gang member”–was able to get a concealed carry permit.

Arquero’s possession of a concealed permit came to police attention after he shot and killed another man in self-defense on September 10.

According to the Associated Press, “Arquero was at a taco stand when 18-year-old Louis Rodriguez opened fire from a passing [vehicle], wounding Arquero.” Arquero then “returned fire” and killed Rodriquez. Although he shot in self-defense, Arquero was “charged with unlawful use of a weapon by a felon and ordered held on $2 million bond.”

The investigation into how Arquero obtained a concealed permit is ongoing. However, Illinois State Police have determined that he has at least one alias and that his gang affiliation is tied to it. Under that same alias–Michael Trivasano–Arquero also has “multiple convictions with gun charges.”

AWR Hawkins is the Second Amendment columnist for Breitbart News and political analyst for Armed American Radio. Follow him on Twitter: @AWRHawkins. Reach him directly at awrhawkins@breitbart.com.