A Florida sheriff’s deputy who fatally shot a Black US air force airman in the military member’s own home has been fired from his job, officials said on Friday.

The Okaloosa county sheriff’s office said it dismissed the deputy, Eddie Duran, after investigators found that his “use of deadly force was not objectively reasonable and therefore violated agency policy” in the killing of senior airman Roger Fortson on 3 May 2024.

The 23-year-old was at his off-base home in Fort Walton Beach when Duran was sent to a disturbance at Fortson’s apartment complex.

Dispatch records put the location of the reported disturbance in apartment 1401. And an employee of the apartment complex told Duran that the disturbance was in apartment 1401 while also claiming that “there had been recent unreported disturbances at or around the same apartment”, Okaloosa sheriff’s officials claimed.

Related: Florida ex-cop with ‘patterns of abuse and bias’ joins DeSantis’s state guard

When Duran arrived at the unit in question, he listened for any noises indicative of a disturbance inside. Duran didn’t hear any, “knocked without announcing” himself as a sheriff’s deputy and kept listening, authorities said.

Duran said that he heard words to the effect of “it’s the fucking police”. Duran knocked “loudly” twice more and said “sheriff’s office” each time, according to the agency’s statement.

Fortson opened the door, with a gun in his right hand. But the sheriff’s office said the gun was “pointed at the ground sufficiently enough for the former deputy to clearly see the rear face of the rear sight”, meaning it was not held in a way that constituted an immediate deadly threat.

Duran confirmed that Fortson “did not physically resist him in any way”. And investigators determined that Fortson did not point the gun in Duran’s direction.

Body camera footage revealed that Duran shot Fortson multiple times two seconds after he opened the door, according to the Associated Press.

Duran claimed to investigators that he perceived aggression in Fortson’s eyes and told them: “I’m standing there thinking, ‘I’m about to get shot, I’m about to die.’” Yet Fortson’s gun was pointed “directly at the ground” – not at Duran, the AP reported.

“This tragic incident should have never occurred,” the Okaloosa county sheriff, Eric Aden, said in a statement. “The objective facts do not support the use of deadly force as an appropriate response to Mr Fortson’s actions. Mr Fortson did not commit any crime. By all accounts, he was an exceptional airman and individual.”

Duran was not facing criminal charges at the time of his firing. But the Florida department of law enforcement is continuing to investigate Fortson’s death, the AP said.

The civil rights attorney representing Fortson’s family, Ben Crump, said Duran’s firing was a “step forward”. But it was “not full justice for Roger and his family”, Crump added

“The actions of this deputy were not just negligent – they were criminal,” Crump said. “As we’ve stated from the beginning, and as echoed today by Sheriff Aden, Roger was an exceptional airman who did absolutely nothing to warrant being gunned down in his own home.

“While the criminal investigation is still ongoing, we fully anticipate charges to be filed against this officer. The video footage provides damning proof that this was a brutal and senseless killing of a young man who was simply enjoying time alone with his dog while video chatting with his girlfriend.”

In prior comments, Crump relayed Fortson’s girlfriend’s account of the deadly shooting. While on the FaceTime call, she said, Fortson asked who was knocking, but there was no answer, according to the AP.

Several moments later, there was a louder knock. He looked through the peephole and didn’t see anybody, Crump told reporters of her account.

Fortson, worried, went to retrieve his legally owned gun. After Fortson was shot, he was on the floor, saying “I can’t breathe,” Crump recounted.

The woman stated that Fortson was not making a disturbance on their call and thought that deputies went to the wrong address, Crump said, according to the AP.