The Illinois State Police said Steven Tiller Jr., 22, was arrested Friday. Prosecutors charged him with first-degree murder and unlawful use of a weapon.
The agency has spent nearly 40 years at Pine Street and North Broadway, occupying the top four floors as one of the foremost PR and marketing firms in the country.
Several local and national organizations over the weekend condemned what they said was a racially motivated attack on a Black off-duty officer by three construction workers last month.
Kyle Gaines, a spokesperson for the ambulance district, said no foul play is suspected and that an autopsy has been completed. The results of the autopsy will not be released for some time.
Developments in some of the St. Louis County's newest suburbs are building "town centers" of entertainment, employment and housing, where there weren't any before.
Steph Kukuljan and Nassim Benchaabane St. Louis Post-Dispatch