They did not say whether he died from being shot by a police sniper during a standoff hours earlier or when police set off controlled explosions of his van at around noon CT.
Police set off the two controlled blasts after saying they found two pipe bombs inside the armoured van, which the shooter used to launch an assault on police HQ at around 12:30 a.m. Saturday.
"We can now confirm that the susp[ect] in the van is deceased but unable to confirm ID pending med ex[aminer] identification," Dallas police Maj. Max Geron tweeted.
"Lots of shrapnel was included in the pipe bombs that exploded — screws, nails."
Police fired at the man around 5 a.m. CT while he was inside the armoured vehicle at a parking lot in suburban Hutchins, south of Dallas, where he had been in a standoff with SWAT team officers.
Police Chief David Brown said a sniper hit the suspect and that officers had lost contact with him for several hours afterward.
Officers were wary of approaching or entering the van, though, because the driver had declared it contained military-grade C4 explosives, they said.
Geron tweeted that a .50-calibre rifle was used to fire two shots into the van's engine block and one into the driver.
Hours earlier, witnesses said, the driver fired several rounds at officers outside the Dallas police headquarters building and rammed his van into a squad car before fleeing.
No one was injured in the gunfire.
"This suspect had already shot at our facility, had rammed a car, shot at officers, and two officers narrowly escaped being shot by the suspect," Brown said. "Then the suspect fled in a vehicle. We chased him."
Shortly after the headquarters shooting, police found four duffel bags scattered around the building, one of which had pipe bombs inside. That bag exploded as a robot attempted to remove it, but no one was injured, Brown said. Nearby residents were told to leave the area, he said.
Brown earlier told reporters police were investigating witness accounts that as many as four individuals may have been firing automatic weapons. However, he later said police believe there is only one suspected shooter. He said a motive was not yet known.
"We barely survived the intent of this suspect," he said.
During the standoff in a fast-food restaurant parking lot in Hutchins, Brown said, police negotiators made contact with the driver, who identified himself as James Boulware. Police have not confirmed his identity.
Brown said Boulware — who had previously been in contact with police in connection with "three different family violence cases" — said at the scene that police had taken his son and had accused him of being a "terrorist." Brown said he then threatened to "blow us up."
A local CBS affiliate interviewed Boulware's father, James, who told reporter J.D. Miles that his son was upset because of a child custody battle he was involved in with his mother because his ex-wife was in prison.
A video of the incident on social media showed a police officer approaching a black van with a flashlight as two other police cruisers pulled up behind the vehicle. The officer then abruptly turned and ran away and then a volley of gunshots could be heard.
In another video, the van could be seen ramming a police cruiser before gunfire rang out and the vehicle drove off.
There are reports the van appears to be outfitted with gun ports in the sides.
Police are reportedly investigating whether it is the same armoured van that was sold on eBay as a "zombie apocalypse assault vehicle" last week.