A man who had fired a gun inside a ticketing area at Houston's largest airport was killed after being confronted by a law enforcement official during an incident that sent people in the terminal scrambling and screaming, police said Thursday.

It's unclear if the unidentified man fatally shot himself or was killed by a Homeland Security agent who had confronted him, said Houston police spokesman Kese Smith.

Police say the man walked into the ticketing area in Terminal B at Bush Intercontinental Airport around 1:35 p.m. and fired at least one shot into the air. The agent, who was in his office, came out and confronted the man, telling him to drop his weapon. The man refused, so the agent shot at him, Smith said.

At the same time the agent was firing, it appeared the gunman was shooting himself, Smith said.

The man died at the scene. An autopsy will be conducted Friday.

Police would not say what kind of weapon the man had.

The terminal was closed, but the rest of the airport was still running. Houston police Capt. Dwayne Ready said the terminal was still an active crime scene and it was unclear when it would be reopen.

Darian Ward, a spokeswoman for the Houston Airport System, said passengers who were scheduled to leave from Terminal B were being rerouted to other terminals.

Dale Howard, of Tomball, was at the baggage handling area of the airport waiting for his sister to arrive on an incoming flight when he heard two shots fired from the floor above. A few seconds later, he said he heard three more shots.

"People were screaming. I knew exactly what it was _ gunfire," Howard said.

Police from an adjacent station rushed in, and Howard said he directed them to the floor above.

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Associated Press writers Juan A. Lozano and Ramit Plushnick-Masti contributed to this report.