SEATTLE (AP) — The Washington State Patrol is seeking help from the public as they investigate a theft of $400,000 in diamonds.

The patrol says a witness reported an attempted carjacking at about 3:48 p.m. Tuesday on the westbound Highway 520 ramp to northbound I-5 in Seattle.

The patrol says responding troopers determined the incident was actually a diamond theft.

The victim told troopers he was driving to see a jeweler-client when a dark sedan changed lanes and slammed on the brakes, causing him to brake and stop.

The man reported that a second vehicle struck his car from behind and two men wearing bandanas approached his vehicle, breaking out windows, striking him and grabbing a bag of diamonds.

The man told troopers the suspects also took his car key, cellphone and a suitcase.

Anyone with information is asked to call Detective Vik Mauro at (425) 401-7746.

In October 2016, masked suspects blocked in gem couriers on a highway ramp near SeaTac. Those suspects also stole $400,00 worth of diamonds from their car. Three men were arrested in connection to the heist in February 2017. Detectives believed those suspects are part of a coordinated criminal organization.

Other similar robberies that occurred in the area between 2016-2017 involved bands of two to four masked men who targeted lone jewel couriers.