Officers established that two to three incendiary devices had been thrown outside and into a Home Office immigration premises by a single suspect who arrived at the scene in a car on Sunday 30 October 2022.
The suspect - a 66-year-old man, was identified, and was located at a nearby petrol station, and confirmed deceased.
The Explosive Ordnance Disposal Unit attended the location to ensure there were no further threats. A further device was found and confirmed safe within the suspect’s vehicle.
Kent Police are also being assisted by Thames Valley Police to carry out a warrant at a property in High Wycombe.
The site remained open, however around 700 suspected migrants were relocated to Manston to ensure safety during the initial phase of the police investigation.
Enquiries into the incident remain ongoing by Kent detectives.