John Bacon, Alan Gomez and Carol McAlice Currie

USA TODAY NETWORK

FORT LAUDERDALE — The man accused of a bloody shooting spree that left five people dead and six wounded at the international airport here faces a court appearance Monday while the motive for his rampage remains a mystery.

Iraq war veteran Esteban Santiago, 26, is accused of an act of violence at an airport resulting in death, along with two firearms offenses. More charges are likely as the investigation into Friday's attack continues.

Yellow caution tape blocked access to some areas of the airport's Terminal 2 on Sunday. The airport returned to full flight operations, but a combination of factors led to long lines for travelers.

Santiago will appear before a federal magistrate on Monday, when he'll get a court-appointed lawyer if he needs one. Authorities investigating the shooting said they had not ruled out a terrorism motive.

George Piro, FBI special agent in charge of the Miami office, has said it was not clear why Santiago decided to fly from his home in Anchorage to carry out the shooting here. Authorities have conducted almost 200 interviews and are scouring social media, digging for clues that might shed light on what prompted so heinous a crime.

TMZ released video that appears to show the suspect drawing a semiautomatic handgun and firing the first shots before he walks out of the camera shot. The website did not reveal the source of the video. Authorities say he gave himself up after running out of ammunition.

Santiago is no stranger to federal law enforcement. In November, he walked into FBI offices in Anchorage and told agents he was a victim of mind control and was being forced to watch Islamic State videos. The FBI conducted a background check and found no connection to terror groups.

Frustrated travelers, 20K lost items as Fla. airport resumes operations

Anchorage police investigated Fla. airport shooting suspect

Santiago was turned over to local law enforcement for a medical referral and released. Neighbors in Anchorage say Santiago and his girlfriend were pleasant enough — until recently.

“We used to watch the mom sit on the front porch and watch her daughter play while she took care of the baby,” said Pamela VanDyke, whose back stairs and stoop face Santiago’s front door. "They seemed to be so happy."

But in October some issues began to develop, said VanDyke's daughter, Brittany Adams. She said Santiago started parking a space designated specifically for her mother because of knee and hip surgeries.

VanDyke and Adams said they tried to reason with Santiago, but he responded "rather darkly." About two weeks ago a neighbor had to call the police because Santiago "was having a loud party and then kicked in his door," Adams said.

"He just seemed to have more parties that got out of hand," she said.

The women wondered if post-traumatic stress combined with seasonal affective disorder could have had an impact on Santiago's mood change. This is a season of extremely long nights in Alaska, and many residents struggle with the limited opportunity for sunshine.

Family members told The New York Times that Santiago was never quite the same after returning from a nine-month tour of Iraq in 2010.

“After Iraq, something happened,” Hernan Rivera, 70, Santiago’s uncle, told the Times. “When he came back from Iraq, he was a different person.”

Greg Homish, a psychiatric epidemiologist and associate professor at the University at Buffalo, says it's too early to know what role PTSD, substance abuse or other factors may have played. Several factors likely contributed, he told USA TODAY.

"This tragedy continues to reinforce the need to provide evaluation and treatment services to current and former members of the military as well as their family members," he said.

On Sunday the airport here was bloated with people trying to rebook flights canceled Friday and Saturday. Most of the baggage claim area at Terminal 2, where the shooting took place, remained walled off as cleanup crews replaced carpets and repaired damage from the shooting.

Adding to the problem was a winter storm that has torn through much of the East Coast, delaying many inbound flights, further delaying flights heading out. Also, several cruise ships returned to Port Everglades just a few miles away, adding a crush of thousands of passengers, many of whom had no idea what had taken place.

"It's a hat trick," said Michael Nonnemacher, director of airport operations. He said it will take a week to get the airport back to normal .

Currie reported from Anchorage, Alaska; Bacon from McLean, Va.