Austin's police bomb squad has been deployed to investigate potential explosive devices, apparently set by a man who opened fire on police headquarters overnight. (Reuters)

A gunman in Austin opened fire Friday on “multiple downtown buildings” — including a federal courthouse, the Mexican consulate and Austin Police Department headquarters — before dying of a gunshot wound, according to officials in the Texas capital. Authorities initially said the man, identified as 49-year-old Larry McQuilliams, had been shot and killed by police, but said later that they were still investigating the possibility that he died of a self-inflicted wound.

Authorities are still investigating a possible motive. But Austin Police Chief Art Acevedo told reporters Friday that, based on his own experience and the suspect’s targets, “the national debate about immigration right now…certainly comes to mind.”

Describing the suspect’s actions as “violent anti-everything behavior, anti-government behavior if you will,” Acevedo said he was willing to speculate that the current “heated” political discourse on immigration issues “might have fed into some of this.”

While firing at the Mexican consulate, the suspect also attempted to “ignite” the building using small cylinders of fuel used by campers, Acevedo said.

The Mexican Foreign Ministry expressed its “deep concern and condemnation of the incident” in a statement, according to Reuters.

Acevedo said McQuilliams had a criminal record.

Austin police said at an earlier news briefing that they had killed the suspected shooter near his vehicle, which officials believed at the time might have contained an explosive device. A bomb squad team investigated both the vehicle and the suspected gunman’s vest, assistant police chief Raul Munguia said at an early morning briefing.

Acevedo, the police chief, later told reporters that both the suspect’s vest and the vehicle were cleared by the bomb squad and that police were still investigating whether the suspect died from police gunfire, from a self-inflicted wound, or from a combination of both.

Shortly before 2:30 a.m. local time, 911 dispatchers started receiving calls about an active shooter in downtown Austin. The gunman targeted the courthouse first, and then the Mexican consulate, before heading to police headquarters, Acevedo said. In all, Acevedo said, McQuilliams fired more than 100 rounds during the shooting spree, police said.

The officer who shot at the suspect in front of the police headquarters was in the process of putting away horses used by the force’s mounted patrols. He held the reins of two horses in one hand when he spotted the suspect near police headquarters, Acevedo said, and took a “one-hand shot” at the suspect with his free hand. If the officer’s fire hit the suspect, Acevedo said, it “would be one heck of a shot.”

The officer is currently on paid administrative leave as police investigate the incident.

As multiple officers approached the suspect to tend to his wounds, they saw what looked like a potential IED in a nearby vehicle. And they saw that McQuilliams was wearing a “suspicious” vest, Acevedo said. Unable to immediately determine whether the vest was “protective” or a “suicide-type” vest, the officers retreated and called in the bomb squad.

The investigation in the Texas capital closed a portion of Interstate 35, the main highway through the city, for hours. It has since reopened. Police also searched the suspect’s residence for explosives.

Hans Paap, who lives near the site of the shooting, told NBC News that he “woke up to a burst of gunfire, heard a second round and then got to the window and saw a third round.” He added that he could “see the muzzle flashes.”

Paap, who manages a nightclub in Austin, told NBC News that there were fewer people on the streets overnight during the time of the shooting because of the Thanksgiving holiday. “On a typical Thursday, Friday or Saturday night, there could have been more people around; but it was very quiet tonight,” he said.

[This post has been updated multiple times.]