A group of up to four gunmen attacked a police station in Texas overnight, firing at officers.
A black van then rammed a police vehicle outside their Dallas headquarters.
Men from inside the armoured van began firing with automatic weapons before fleeing the scene.
A bomb was later discovered outside the building, which exploded when examined by a police robot. There are no reports of injuries.
Another video showed a police officer approaching the vehicle and then fleeing when he realised the threat. A large number of shots are subsequently heard.
Police pursued the vehicle, said to be armoured with firing holes cut into its sides.
When the van stopped in a fast food restaurant parking lot in the city of Hutchins there was an exchange of fire.
Dallas police chief David Brown said at a press conference that one of the suspects had identified himself to local residents as James Boulware.
He said police had taken his son and accused him of being a terrorist.
Gunmen attacked Dallas Police headquarters on Saturday (June 13) morning and an explosive device was later found outside the building.
A stand-off is continuing between the gunmen and police.
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