PENUELAS, Puerto Rico -- The brother of a man accused of killing five people at a Florida airport questioned Saturday why his brother was allowed to keep his gun after U.S. authorities knew he'd become increasingly paranoid and was hearing voices.

Esteban Santiago, 26, had trouble controlling his anger after serving in Iraq and told his brother he felt he was being chased and controlled by the CIA through secret online messages.

When he told agents at an FBI office his paranoid thoughts in November, he was evaluated for four days and released without follow-up medication or therapy.

"The FBI failed there," Bryan Santiago said. "We're not talking about someone who emerged from anonymity to do something like this."

Speaking outside his family's house in Penuelas, the brother said: "The federal government already knew about this for months, they had been evaluating him for a while, but they didn't do anything."

Bryan Santiago said he saw his brother was behaving differently when he returned from Iraq.

"He sometimes couldn't control his anger," he said. "You could tell something had changed."

Bryan Santiago said when he went to visit his brother in Alaska in August, he said Santiago told him he was hearing voices and felt he was being chased.

Authorities in Alaska on Saturday defended their interactions with Esteban Santiago. FBI special agent in charge Marlin Ritzman said Santiago broke no laws when he walked into the Anchorage FBI office "making disjointed comments about mind control."

He characterized Santiago as a "walk-in complaint," which he said offices receive daily.

Anchorage police were called to the office by the agency, was told Santiago was having "terroristic thoughts" and believed he was being influenced by the Islamic State group and was taken to a mental health facility, city police chief Chris Tolley said.

Santiago had left a gun and his newborn child in his vehicle when he went to the FBI office. Police held the gun until Santiago was released and contacted him about picking up the weapon, which he did Dec. 8, Tolley said.

"There is speculation that it is the same gun. I have not received confirmation that it, in fact, is that gun," Tolley said.

In recent years, Esteban Santiago had been living in Anchorage. But there were signs of trouble.

He was charged in a domestic violence case in January 2016, damaging a door when he forced his way into a bathroom at his girlfriend's Anchorage home. The woman said he yelled at her to leave, choked her and smacked her on the side of the head, according to charging documents.

A month later, municipal prosecutors said he violated the conditions of his release when officers found him at her home during a routine check. He told police he had lived there since he was released from custody the previous month. His Anchorage lawyer, Max Holmquist, declined to discuss his client.

Tolley detailed other complaints of physical disturbances last year involving Santiago but said officers found no probable cause for arrest or were told by the city prosecutor not to arrest him.

Bryan Santiago said his brother had requested psychological help but barely received any.

"I told him to go to church or to seek professional help," he said.

Family members have said Esteban Santiago changed after serving a yearlong tour in Iraq. He was born in New Jersey but moved to Puerto Rico when he was 2, his brother said. He grew up in Penuelas before joining the Guard in 2007.

He deployed in 2010 as part of the Puerto Rico National Guard, spending a year with an engineering battalion, according to Guard spokesman Maj. Paul Dahlen.

Esteban Santiago's mother wiped tears from her eyes as she stood inside a screen door Saturday. She said her son had been affected tremendously by seeing a bomb explode near two friends while serving in Iraq.

Alaska National Guard spokeswoman Lt. Col. Candis Olmstead told The New York Times two soldiers in Santiago's company had died during his stint in Iraq.

Former neighbor Ursula Candelario in Penuelas recalled seeing Esteban Santiago grow up and said people used to salute him after he joined the Guard.

"He was very peaceful, very educated, very serious," she said. "We're in shock. I couldn't believe it."

Since returning from Iraq, Santiago served in the Army Reserves and the Alaska National Guard in Anchorage, Olmstead said. He was serving as a combat engineer in the Guard before his discharge for "unsatisfactory performance." His military rank upon discharge was E3, private 1st class, and he worked one weekend a month with an additional 15 days of training yearly, Olmstead said.

She would not elaborate on his discharge. The Pentagon said he went AWOL several times and was demoted and discharged.

While it is unclear whether Esteban Santiago had been diagnosed with post-traumatic stress disorder, as many as one in five veterans who served in Iraq or Afghanistan develop the affliction each year, according to the U.S. Department of Veterans Affairs. A 2014 Veterans Affairs study found almost 30 percent of veterans returning from Iraq and Afghanistan who sought treatment at VA hospitals were diagnosed with PTSD symptoms.

His uncle and aunt in New Jersey were trying to make sense of what they were hearing about Santiago. FBI agents arrived at their house to question them Friday.

Maria Ruiz told The Record newspaper her nephew had recently become a father to a son and was struggling.

"It was like he lost his mind," she said in Spanish of his return from Iraq. "He said he saw things."

Santiago was flying from Anchorage on a Delta flight and had checked only one piece of luggage, which contained the gun.

Sen.-elect Nelson Cruz, who knew the family and represents the town where they live in Puerto Rico, said he had been talking regularly with Bryan Santiago since the shooting.

"They're very humble and very Christian people," Cruz said. "They want to tell the families of the victims that they're extremely saddened and extremely upset by what happened."