It happened at around 2.40pm on Tuesday, May 17. A silver Honda Civic was driving London bound on the A12 near Ingatestone when a stone hit the car. It may have been thrown from the bridge which runs over the A12. It caused damage to the windscreen. The driver and his passenger were not injured but were left very shaken after the incident.
Officers would like to hear from anybody who may have witnessed anybody acting suspiciously in the area or on the bridge around the time of the incident.
Anybody that can help is asked to call Pc Thomas Buchanan at Brentwood on Essex Police 101 or Crimestoppers anonymously on 0800 555 111.