It's unclear if the man, identified by the FBI as 29-year-old Carnell Moore of Beaumont, fatally shot himself or was killed by a Homeland Security agent who had confronted him.
According to authorities, Moore left behind a suicide note, in which he said he didn't want to hurt anyone, but that, "The monster within is getting stronger."
It was around 1:35pm Thursday that Houston police say they were called to a "discharge of firearm" at Terminal B.
Police say Moore walked into the ticketing area in Terminal B at Bush Intercontinental Airport and fired at least one shot into the air. The agent, who was in his office, came out and confronted Moore, telling him to drop his weapon, but he refused, police said.
"The suspect then turned toward the special agent. The special agent, fearing for his safety and all the passengers in the terminal, discharged his weapon at the same time it appears the suspect may have shot himself," Houston police spokesman Kese Smith said.
Moore died at the scene. An autopsy will be conducted Friday. The Department of Homeland Security said the agent was not injured in the shooting, but he was transported to a local hospital as a precautionary measure.
Police say they recovered Moore's handgun from the scene and found a rifle inside a truck believed to belong to him. They also say they found a suicide note that says he is taking his life because "the monster within is getting stronger."
Authorities say Moore was staying at a hotel in Houston. Meanwhile, FBI officials are at Moore's home in Beaumont, gathering any evidence there.
Moore was quite vocal about his intentions, even posting some eerie messages on Facebook. On Wednesday, Moore wrote, "I recently had the chance of staring death in the face, and she was beautiful."
A few hours later, Moore posted, "this life will crash tomorrow."
Terminal B was shut down for several hours during the investigation and passengers were being sent to other terminals, according to the Houston Airport System. It reopened around 5:30pm.
Witnesses tell ABC13 they heard a couple of gunshots ring out and a TSA agent told everyone to get down.
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.
Greg Newburn, who was in the terminal waiting for a flight to Oklahoma City, said he was sitting in a cafe area when he heard two gunshots and after a pause, several more.
"It seemed like quite a few shots. Everyone was scrambling, running left and running right, turning tables up and hiding behind tables. Nobody knew what was happening. I couldn't tell where the shots were coming from," he said.
Newburn, from Gainesville, Fla., said it took him a few seconds to realize that the shots had come from the terminal ticketing area, near the security checkpoint. Newburn said he didn't see who had fired the shots.
Just last month, United Airlines unveiled the newly renovated Terminal B at IAH. The new 225,000 square foot South Concourse is four times larger than the previous facility and is used for United Express regional flights.
HOW COULD IT HAPPEN?
We asked our security analyst how someone could get weapons into an airport terminal. Jim Conway says there are no metal detectors or screenings between the terminal entrances and security checkpoints.
"Obviously, security at the terminal building is going to be higher at the Galleria or an Edwards Theater or something like that," he said. "But it is still considered by security folk as a public area and people can freely move in and out of there with weapons, too."
Conway also says airport security officers are more focused on people who are going to be boarding aircraft than the other people in airport terminals.
MAYOR PARKER TWEETS
In the hours following the shooting, Houston Mayor Annise Parker praised law enforcement officers on the scene, tweeting "Shooting incident at IAH under control. Police acted swiftly. System in place worked. Glad no other injuries. Airport open, check "at IAH".
The Associated Press contributed to this report.
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