The motive for the stabbing by the Erasmus bridge a week ago, in which one man died and a second was injured, remains unclear, Rotterdam mayor Ahmed Aboutaleb said on Thursday.

Speaking during his last council meeting as mayor, Aboutaleb said many questions about the incident still remain unanswered. For example, he said, it is unclear why the man went to Rotterdam from his home in Amersfoort and where he got hold of the knives.

The public prosecution department has said the killing may have been a terrorist incident. Witnesses said the man shouted “Allahu akbar” as he attacked.

Since then it has emerged that the suspect Ayoub M has a psychiatric illness and had earlier tried to kill his mother. He has also undergone treatment in a secure unit.

M’s victim was German national, Philipp Winter, who had moved to Rotterdam six months earlier to pursue his dream job. A 33-year-old Swiss national who was also wounded in the attack was released from hospital on Sunday after being treated for his injuries.

Carola Schouten, the former farm minister and a ChristenUnie stalwart, takes over as Rotterdam mayor on October 10.