The incident happened on West Avenue shortly before 5 p.m. Saturday, Aug. 1.
No injuries have been reported, police said.
A significant portion of West Avenue between Leroy Avenue and Noroton Avenue will be closed as investigators process the crime scene.
A heavy police presence should be expected in the area and motorists should seek alternate routes, police said.
"We are confident that there is no threat to area residents at this time," Darien Police said.
If anyone has information regarding this incident, please contact the Darien Police Department at 203-662-5300.
Click here to follow Daily Voice Newtown and receive free news updates.