Police are continuing to question two suspects who were arrested after a customer was stabbed to death inside a bank in Derby.
A cordon was set up in the area around the Lloyds branch in St Peter's Street after a man his 30s died at the scene following the attack shortly before 14.30 BST on Tuesday.
Derbyshire Police later arrested a man in his 40s on suspicion of murder and another in his 30s on suspicion of assisting an offender.
Supt Rebecca Webster said both suspects remain in custody and were being questioned by officers working on the murder investigation.
"This is an absolutely devastating incident in the heart of our city," she said.
"For the family of the victim, we know that life will never be the same again and our thoughts are with them as they begin to deal with their tragic loss.
"Those who witnessed the incident and offered first aid and tried to help at the scene will also be understandably devastated by what happened.
"And there will of course be the impact on the wider community from such a shocking event.
"Officers have worked through the night on this investigation and two men were arrested yesterday and they remain in police custody."
Supt Webster said the police cordon, which stretches into nearby East Street, was likely to remain in place for a large part of Wednesday.
The victim's family have been informed of his death.
Lloyds has said it is "deeply saddened" by the incident, while Labour MPs Catherine Atkinson and Baggy Shanker, who represent Derby North and Derby South respectively, said they had contacted emergency services "to offer our support".
"This is a tragic and shocking incident," they added. "Violence has no place in our community."
Brad Worley, BID manager for St Peters Quarter Business Improvement District, said rangers would remain in the area to provide support and assistance in any way they can.
He added: "We are deeply shocked and saddened by the tragic incident that took place on Tuesday at Lloyds Bank in St Peter's Street, in which a man lost his life.
"Our thoughts at this unimaginably difficult time are first and foremost with the victim's family and loved ones.
"As a community, we will continue to stand together in the face of tragedy and continue our work for a safer, stronger city centre for all."