Update:Dallas police have shot the suspect after a standoff and now believe he acted alone.
DALLAS -- Multiple gunmen toting automatic weapons opened fire on officers outside Dallas Police headquarters early Saturday morning, before one man fled the scene in what witnesses described as an armored van, according to Dallas Police Chief David Brown.
Police said conflicting witness accounts made it difficult to immediately determine how many shooters were involved and authorities were trying to determine a motive.
Brown said during a news conference that the shootout began about 12:30 a.m. Saturday, when the suspects parked in front of the building located south of downtown and began firing. He said at least one of the suspects fled the scene in a van that rammed a police cruiser before leading police on a chase that ended in an ongoing standoff at parking lot in the nearby suburb of Hutchins, where additional gunfire was exchanged.
Brown said the suspect driving the van has told officers that he blames police for losing custody of his son and "accused him of being a terrorist." The gunman also said he had explosives in the van, which appeared to be outfitted with gun ports in the sides.
Police said that the man has given them his name, but they have not been able to confirm his identity, CBS News correspondent Vicente Arenas reports from Dallas. The name given by the suspect has been associated with three cases of domestic violence.
Brown said negotiations with that suspect and the SWAT unit are ongoing. No injuries were reported.
On Twitter, police said SWAT officers "disabled" the vehicle.
Brown said, based on witness accounts, as many as four suspects may have been involved in the original shooting, including some who may have been strategically positioned at elevated positions. Police could not immediately confirm how many shooters were involved and where any additional suspects may be located.
Meanwhile, Brown said police also found four bags outside police headquarters, including one that held a pipe bomb that later exploded.
Later Saturday morning, the police department tweeted that two explosive devices had been found and that all suspected packages had been cleared.
Ladarrick Alexander and his fiancée, Laquita Davis, were driving back toward the police station to their nearby apartment when they heard 15 to 20 gunshots in quick succession.
Seconds later, police could be seen swarming an unmarked van that appeared to have crashed into a police car, they said.
They turned around and were parked outside the police perimeter about two blocks away, where they heard the sound of one detonation at about 4:30 a.m. and smoke coming up in the air.
Police headquarters is in a former warehouse district where a boutique hotel and several new apartment buildings have been opened.
"We don't see too much going around here at all," Alexander said.