“Our thoughts are with Andre’s family, who we also want to support during this difficult time,” the fire department said in a statement.
The youth fire brigade of Lower Saxony also paid tribute to the nine-year-old.
“Our condolences to his family, friends and all who were close to him,” the statement said.
“We support them in this difficult time and express our deepest sympathies,” the statement added.
More than 200 people were injured in Friday’s attack, some of them in critical condition.
The four women who were also killed have not yet been identified.