Shots fired at Dallas police headquarters
Grainy footage showed the van, left, being chased by police Shots have been fired at the police headquarters in Dallas, and a suspect has fled the scene in what witnesses say was as an armoured van.
Dozens of police cars gave chase and the man is now involved in a stand-off in a car park, officials said.
There has been an exchange of gunfire in the car park, they added.
Four bags were left outside the police headquarters, one of which contained explosives including pipe bombs, [Only registered and activated users can see links. ]
A later statement said one of the bags exploded as experts tried to move it.
The motive for the shooting is not yet clear. Dallas police say no police officers have been injured.
Dallas Police Chief David Brown quoted witnesses as saying that as many as four suspects were involved in the initial shooting incident.
He said officers were negotiating with the occupant of the van which is in a car park in Hutchins, about nine miles (14km) from central Dallas.
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