Peter Bjurbo, a reporter at national Swedish broadcaster Sveriges Radio, was at a restaurant nearby when the devastating incident took place.
Speaking to LBC’s Shelagh Fogarty, the witness said it was “obvious” it was not an accident.
He said: “I was sitting at the restaurant 150 meters from the scene. Suddenly people were screaming, they were shocked.
“People were walking to do their Friday shopping, then I saw a dead dog and I saw some dead people lying on the street.
A lorry crashed into a department store this afternoon killing at least three people
It was quite obvious that it was not an accident, that it was intentional, yes
“And then I heard that a lorry had been going in a very high speed towards a shop, a big shop called Åhlens and it appeared that it go into the shop Åhlens.”
He said it was clear that the crash was “intentional” and said that members of the public had heard shots before the smash.
Mr Bjurbo said: “It was quite obvious that it was not an accident, that it was intentional, yes.
“I spoke to people who said that they were shooting from the lorry and people told me that they heard a lot of shots before the lorry entered the shop Åhlens.
LIVE IMAGES: SWEDEN TERROR Fri, April 7, 2017
The vehicle drove into crowds on Drottninggatan (Queen Street) – one of the city's major pedestrian streets, just before 3pm local time, before crashing into Åhlens Mall
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Truck rams into crowds in central Stockholm
The eyewitness said it was "obvious" the crash was deliberate
“There are people telling me that the fire alarm inside the shop Åhlens went off just before the lorry hit the shop, I’m not sure that is conformed fact.”
The vehicle drove into crowds on Drottninggatan (Queen Street) – one of the city's major pedestrian streets, just before 3pm local time, before crashing into Åhlens Mall.
Armed police are currently at the scene and the incident is being treated as a suspected terror attack, according to local media.
The lorry had been hijacked earlier in the day.
The public has been warned to stay away from the city centre and a police cordon has been put up around the area.
Swedish Prime Minister Stefan Lofven has said everything indicates that the Stockholm truck crash is "a terror attack".
He added: “The Government is naturally being updated continuously and receiving the latest information.
“The Government is assisting the authorities in its work and now we are encouraging the public to be alert and listen to the police’s information.”
At least two people have been arrested by police – the first arrest was made at Olof Palmes gata and the other at Klara North Church Street.