Officials arrested a suspect — a 37-year-old Turkish-born man — after an eight-hour manhunt, but it’s unclear whether he was the only person involved in the attack.

The authorities said they were looking into the possibility the shooting was an act of terrorism, with the country’s counterterrorism agency raising its threat assessment to the highest level. They also ordered the evacuation of all mosques in the city, but it was unclear whether that move stemmed from a specific threat or as a precaution in the wake of the attack in New Zealand. The authorities didn’t rule out other motives, and some reports suggested that the attack was a result of a domestic dispute.

Context: Utrecht, a city of 330,000, has a large immigrant population, with more than 30 percent of residents born outside the Netherlands. The attack took place in the Kanaleneiland neighborhood, which is home to a large number of Muslims, including immigrants from Morocco and Turkey.