The suspect in the Fort Lauderdale airport shooting that claimed five lives was a mentally troubled national guard veteran who served a year in Iraq and was later discharged from military service “for unsatisfactory performance”, officials said on Friday.

Members of Esteban Santiago’s family told reporters the 26-year-old “lost his mind” after his tour of duty, and had recently received psychological treatment following a number of incidents. In one last summer, he turned up unexpectedly at an FBI office near his home in Anchorage, Alaska, and claimed to be hearing voices in his head telling him to join Isis.

A family photo of Esteban Santiago, 26, the alleged gunman who killed at least five people at Fort Lauderdale airport. Photograph: ddp USA/REX/Shutterstock

According to Maj Paul Dahlen, spokesman for the Puerto Rico National Guard, Santiago was deployed to Iraq in 2010 with the 130th engineer battalion. He later joined the Alaska national guard as an army reservist in November 2014 and was discharged in August 2016, Lt Col Candis Olmstead said, without giving full details.

Santiago was carrying military ID when he was arrested, law enforcement officials said.

Family members said Santiago, who was born in New Jersey but moved to Puerto Rico with his parents as a two-year-old, and then moved to Alaska after his Iraq tour, had been hospitalized or received treatment for mental issues on several occasions.

“Something got to him. It looks like he lost his mind,” his aunt, Maria Ruiz Rivera, told NJ.com in Spanish during a short interview Friday at her apartment in Union City, New Jersey. “He would say that he would see things. So he went to the hospital.”

Her husband, Hernan Rivera, said: “Only thing I could tell you is when he came out of Iraq he wasn’t feeling too good.”

Ruiz Rivera said the last time she saw her nephew was in 2011 when he was “in therapy”. But she said she spoke to him by phone after his baby was born in Alaska in September.

“Everything was fine. He was happy with his baby. He sent me a photo; then I didn’t hear anything more,” she said.

Other family members painted a picture of a troubled young father. Bryan Santiago, the suspect’s brother, confirmed he had a girlfriend and young child in Alaska.

Esteban Santiago’s uncle Hernan Rivera: ‘Only thing I could tell you is when he came out of Iraq he wasn’t feeling too good.’ Photograph: ddp USA/REX/Shutterstock

He said his brother’s girlfriend told him the couple had been fighting and that he had been receiving psychological counselling in Alaska, although he did not know the details. He said he had not heard from his brother “in several weeks”, which he said was unusual, and that his family was worried about him.

“He is a regular person, spiritual, a good person,” Bryan Santiago said in the phone interview, adding that he had been “fighting with a lot of people” in Alaska. He speculated that his brother might have experienced a “flashback” to his military service, although he said the discharge was not due to PTSD or other issues related to his service in Iraq.

He also said that his brother was hospitalized with mental issues after returning from Iraq, and then spent some time in Puerto Rico caring for his sick father before moving to Alaska after his father’s death.

Esteban Santiago also reportedly had a valid Florida’s driver’s license and had an address in Naples, Florida, although officials would not confirm any details about the suspect at a Friday afternoon press conference, citing the continuing investigation.

Public records of Santiago’s history show that he had faced two minor criminal charges, one of operating a vehicle without tailgates, licenses and insurance in 2015, and a misdemeanor charge of violating conditions of release, which was dismissed by prosecutors in 2016.

The Associated Press contributed reporting