WASHINGTON  — A Pentagon police officer died after being stabbed Tuesday during a burst of violence at a transit center outside the building, and a suspect was shot by law enforcement and died at the scene.

The Pentagon, the headquarters of the U.S. military, was temporarily placed on lockdown after a man attacked the officer on a bus platform shortly after 10:30 a.m. The ensuing violence, which included a volley of gunshots, resulted in “several casualties,” said Woodrow Kusse, the chief of the Pentagon Force Protection Agency, which is responsible for security in the facility.

The deaths of the officer and the suspect were first confirmed by officials who were not authorized to discuss the matter and spoke to The Associated Press on condition of anonymity. The Fairfax County Police Department also tweeted condolences about the officer's death. Officials said they believe two bystanders were injured.

The suspect was identified by multiple law enforcement officials as Austin William Lanz, 27, of Georgia.

The officer was ambushed by Lanz, who ran at him and stabbed him in the neck, according to two of the law enforcement officials. Responding officers then shot and killed Lanz. Investigators were still trying to determine a motive for the attack and were digging into Lanz’s background, including any potential history of mental illness or any reason he might want to target the Pentagon or police officers.

The officials could not discuss the investigation publicly and spoke to The AP on condition of anonymity.

Lanz had enlisted in the U.S. Marine Corps in October 2012 but was “administratively separated” less than a month later and never earned the title Marine, the Corps said in a statement.

Lanz was arrested in April in Cobb County, Georgia, on criminal trespassing and burglary charges, according to online court records. The same day, a separate criminal case was filed against Lanz with six additional charges, including two counts of aggravated battery on police, a count of making a terrorist threat and a charge for rioting in a penal institution, the records show.

A judge reduced his bond in May to $30,000 and released him, imposing some conditions, including that he not ingest illegal drugs and that he undergo a mental health evaluation. The charges against him were still listed as pending. A spokesman for the Cobb County Sheriff’s Office confirmed that Lanz had been previously held at the agency’s detention center but referred all other questions to the FBI’s field office in Washington.

An attorney who represented Lanz in the Georgia cases didn’t immediately respond to a phone message and email seeking comment, and messages left with family members at Lanz’s home in the Atlanta suburb of Acworth, Georgia, were not immediately returned.

Tuesday's attack on a busy stretch of the Washington area’s transportation system jangled the nerves of a region already primed to be on high alert for violence and potential intruders outside federal government buildings, particularly following the Jan. 6 riot at the Capitol.

At a Pentagon news conference, Kusse declined to confirm that the officer had been killed or provide even basic information about how the violence had unfolded or how many might be dead. He would only say that an officer had been attacked and that “gunfire was exchanged.”

Kusse and other officials declined to rule out terrorism or provide any other potential motive. But Kusse said the Pentagon complex was secure and "we are not actively looking for another suspect at this time.” He said the FBI was leading the investigation.

“I can’t compromise the ongoing investigation,” Kusse said.

The FBI confirmed only that it was investigating and there was “no ongoing threat to the public” but declined to offer details or a possible motive.

Later Tuesday, the Pentagon Force Protection Agency issued a statement confirming the loss of the officer, and Defense Secretary Lloyd Austin expressed his condolences and said flags at the Pentagon will be flown at half-staff.

“This fallen officer died in the line of duty, helping protect the tens of thousands of people who work in — and who visit — the Pentagon on a daily basis,” Austin said in a statement. “This tragic death today is a stark reminder of the dangers they face and the sacrifices they make. We are forever grateful for that service and the courage with which it is rendered.”

Tuesday's violence occurred on a Metro bus platform that is part of the Pentagon Transit Center, a hub for subway and bus lines. The station is steps from the Pentagon building, which is in Arlington County, Virginia, just across the Potomac River from Washington.

An Associated Press reporter near the building heard multiple gunshots, then a pause, then at least one additional shot. Another AP journalist heard police yelling “shooter.”

A Pentagon announcement said the facility was on lockdown, but that was lifted after noon, except for the area around the crime scene.

Austin and Gen. Mark Milley, chairman of the Joint Chiefs of Staff, were at the White House meeting with President Joe Biden at the time of the shooting. Pentagon spokesman John Kirby said Austin returned to the building and went to the Pentagon police operations center to speak to the officers there.

It was not immediately clear whether any additional security measures might be instituted in the area.

In 2010, two officers with the Pentagon Force Protection Agency were wounded when a gunman approached them at a security screening area. The officers, who survived, returned fire, fatally wounding the gunman, identified as John Patrick Bedell.