IOPC director Derrick Campbell said: “Our sympathies remain with the family of Sean Fitzgerald and all those affected by his death.
“This has been one of the most detailed, complex investigations we’ve carried out in recent years and involved a huge amount of evidence gathering and examination of sensitive intelligence.
“The determination over whether the officer should face disciplinary proceedings largely came down to a split-second decision in what was a dynamic, fast-moving, armed police operation.”
In light of new evidence, the IOPC said it believed it would no longer be reasonable for a disciplinary panel to conclude that the phone held by Fitzgerald was obscured from view until after the decision to shoot had been taken.
It also said there was insufficient evidence that the officer did not see the phone and experts were unanimous in explaining how a black mobile phone could be mistaken for a gun in the circumstances.
Campbell said: “Our conclusion was that the officer has no case to answer for gross misconduct, but I acknowledge Mr Fitzgerald’s family did not agree with our opinion.
“We have reached this position after extensive analysis and careful consideration of whether the evidence now meets the legal threshold we are required to apply.”
He added: “We are extremely conscious of the time taken to reach the current position and we are sorry for any distress this has caused.”
Campbell also emphasised that while it was relatively rare for firearms officers to discharge their weapons, and rarer still for someone to die as a result, there must be proper investigation and accountability when it happened.
The IOPC’s investigation also looked at the planning and implementation of the firearms operation and all of the officers who were directly involved in that were treated as witnesses throughout.