Several people were injured in a shootout at school in the town of Grasse in southern France on Thursday, prompting the country to issue a terror warning. A 17-year-old student carrying several weapons opened fire on the headmaster of the Alexis de Tocqueville school, The Telegraph reported. The police later arrested the student. Initial reports suggest that police believed there was another suspect, who is on the run, The Guardian reported.

Christian Estrosi, president of the Provence-Alpes-Côte d’Azur region said the headmaster’s injuries were minor. The Grasse town hall said the shooting was the result of an altercation between two students. The French interior ministry said it would provide more information soon and that security operations were being carried out.

The terror warning was sent out through the French government’s phone app. Earlier in the day, a letter bomb had exploded at the headquarters of the International Monetary Fund in Paris. No casualties were reported.

The country has been on edge since a terror attack in November 2015 left 134 people dead in Paris.