"He was a loyal father, husband, son, brother, uncle and friend and loved by all who knew him.
His death to leave such a huge hole in our lives and we will be deeply missed by all.
"Words cannot quite describe what life would be like without him. There is so much life left to live and he will be in our hearts and minds every day."
Mr. Duncan was an in-house lawyer for the multinational shipping company.
According to his LinkedIn profile, he was an electrical engineer before he trained as a lawyer at Northumbria University in 2003.
He worked in Newcastle for Royal IHC Limited, which has a city center office close to where it was attacked.
Superintendent Ged Noble, commander of the Northumbria Police Department, said: "This is still an extremely difficult time for Peter's family and loved ones and we ask that their privacy be respected.
"We know that these types of incidents can have a huge impact on the local community.
"I want to reassure the public and businesses that we are doing everything we can to prevent incidents of this tragic nature and ensure that people feel safe.
"I also want to thank those who came forward with the information and for the patience of the public during our investigation."