Utrecht, March 18 -- A gunman killed three people and wounded nine others on a tram in the central Dutch city of Utrecht, sparking a manhunt that saw heavily armed officers with sniffer dogs zero in on an apartment building close to the shooting.

Authorities immediately raised the terror alert for the area to the maximum level, and the city's mayor said a "terror motive" was the most likely theory. Dutch military police went on extra alert at Dutch airports and at key buildings in the country as the Utrecht manhunt took place.

A few hours after the shooting, Utrecht police released a photo of a 37-year-old man born in Turkey who they said was "associated with the incident." The photo showed a bearded man on board a tram, dressed in a da...