the suspect had driven 100 miles to the immigration centre before lobbing several bombs - one of which did not go off - before fleeing.
Dramatic photos show one of the bombs - apparently a lit firework taped to a plastic canister.
Local Gary Smith, 31, claimed the driver was laughing as he flung them out of the window.
He said: “I was walking over a nearby bridge and I could see him throwing the bombs.
“They were making loud bangs. I think he threw about four or five.
“He was just laughing while he was doing it. It was crazy."
Another witness told KentOnline: "I heard what I thought was cannons going off and thought it must have been an event.
"We paused the TV to hear. There were at least six or seven.
"To think it was actually explosions that we heard is just so upsetting."
Police confirmed two minor injuries from the arson attack.
Minister Mark Spencer this morning confirmed that people had been moved from the centre following the attack.
Sources have suggested the incident was not terror-related, with initial inquiries suggesting the man had a history of mental health problems.
Shocking video taken by a witness shows flames engulfing the side of a building.
Terrified people are seen running in the background as cops usher them out of the way.
Around 700 migrants were evacuated amid the drama.
A bomb disposal squad was then spotted near a BP garage, where police officers were seen examining a white SUV.
'Deeply shocked'
Witnesses said the driver took his own life there, leaving staff traumatised.
One stunned worker said: “I swapped shifts with the two people who were on at the time.
“They just wanted to get home, I don’t blame them. They looked really upset.
“When I was walking in, I couldn’t even look at the spot where it happened - I wouldn’t sleep for days.”
Home Secretary Suella Braverman said she was receiving regular updates on the "distressing incident".
She tweeted: "My thoughts are with those affected, the tireless Home Office staff and police responding. We must now support those officers as they carry out their investigation."
Dover and Deal MP Natalie Elphicke tweeted: "I am deeply shocked by the incident in Dover.
"I have spoken to the immigration minister about the situation. My thoughts are with everyone involved."
Kent Police said: "Officers established that two to three incendiary devices had been thrown into a Home Office immigration premises by a single suspect who arrived at the scene in a car.
"Two people have reported minor injuries from inside the property.
"The suspect was identified and very quickly 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.
"The site remained open, however around 700 suspected migrants were relocated to Manston to ensure safety during the initial phase of the police investigation."