At least five people have reportedly died, while eight others were injured, following a shooting at Fort Lauderdale/Hollywood International Airport in south Florida.
The Broward County Sheriff's Office confirmed that one suspect was in custody shortly after the incident in the Terminal 2 baggage claim area.
Authorities investigated reports of a second shooting at the airport, but found no evidence of such an attack.
Florida Sen Bill Nelson said the suspect had been identified as New Jersey-native Esteban Santiago. According to Mr Nelson, the 26-year-old suspect was carrying a military ID.
US officials said the suspect was a passenger on a Canadian flight and carried a checked gun.
Barbara Sharief, mayor of Broward County, said the shooter acted alone.
"We have no evidence at this time that he was acting with anyone else," she told CNN. "He is currently in custody and we're investigating."
Investigators have not yet determined a motive for the shooting.
A witness told NBC that the shooter laid down "spread eagle", and was on the ground for "10 to 15 minutes" before the first police officers arrived.
Eyewitness Mike Starobinsky told ABC News that he heard "popping noises" in the terminal. He grabbed his children and took them to meet family in the neighbouring Terminal 3 when he saw a victim outside "bleeding profusely".
Mr Starobinsky took a photograph of the scene outside the terminal that showed a woman giving aid to the bloody victim.
Former White House press secretary for the George W Bush administration Ari Fleischer was at the airport at the time of the shooting. He tweeted early reports of the incident.
"I'm at the Ft Lauderdale Airport. Shots have been fired," he wrote. "Everyone is running."
He later added: "All seems calm now, but the police aren't letting anyone out of the airport – at least not the area where I am."
Passengers and employees were evacuated from the terminal onto the tarmac, but are slowly returning to the inside of the airport.
"We were told to hit the deck and we stayed there until we were given the green light to leave," a traveller who was at the airport, Bob Foster, told MSNBC. "Needless to say, everybody's pretty shaken up."
Airport officials tweeted: "All services are temporarily suspended at #FLL. Please contact your air carrier about your flight information."
Florida Gov Rick Scott is travelling to Ft Lauderdale to be briefed by law enforcement. State authorities have not confirmed information regarding fatalities or injuries prior to Mr Scott's expected arrival.
Agents form the Bureau of Alcohol, Tobacco, Firearms and Explosives are present to assist state and local law enforcement in their investigation.
Ft Lauderdale/Hollywood International Airport sees some 73,000 passengers pass through daily.
