It happened just after the start of the 4 p.m. newscast downtown.
A male suspect took a large rock out of a plastic bag and threw it against the window.
After a few seconds, he picked up the rock and threw it again.
The glass partially broke.
No one was hurt.
The suspect then walked off, heading north on State Street.
He's described as having a thin build, weighing about 150 pounds and having salt and pepper hair.
Detectives are investigating the incident as criminal damage to property at a commercial business.