Gun was given back to Florida shooting suspect last month

FORT LAUDERDALE, Fla. (Reuters) - Police in Alaska took a handgun from the man accused of killing five people at Fort Lauderdale's airport on Friday, but they returned it to him last month after a medical evaluation found he was not mentally ill, authorities said on Saturday.

Esteban Santiago, a 26-year-old Iraq war veteran, had a history of acting erratically and investigators are probing whether mental illness played a role in the latest U.S. mass shooting. According to court papers, he told agents he planned the attack and bought a one-way ticket to Florida.

Santiago was charged on Saturday in federal court and could potentially face the death penalty if convicted in the case, U.S. prosecutors said.

Marlin Ritzman, special agent in charge of the Federal Bureau of Investigation's office in Anchorage, told a news conference Santiago walked into the office in November and said his mind was being controlled by a U.S. intelligence agency. He was turned over to local police, who took him to a medical facility for a mental evaluation.

"Santiago was having terroristic thoughts and believed he was being influenced by ISIS (the Islamic State militant group,)" Anchorage Police Chief Chris Tolley told the news conference.

A handgun police took from Santiago during the evaluation was returned to him early last month, Tolley told reporters. The police chief said it was not clear if it was the same weapon used on Friday.