BRUSSELS — Three people were shot dead and a fourth seriously wounded Saturday in an armed attack at the Jewish Museum of Belgium in Brussels, officials said. Police detained one suspect and were looking for a second.The bloodshed, on the eve of national and European Parliament elections, led officials to immediately raise anti-terror measures.Belgian Foreign Minister Didier Reynders, who was in the vicinity, said the scene “was terrible and left me shocked” as he saw two bodies lying at the entrance of the museum.Interior Minister Joelle Milquet told reporters that the shooter apparently parked a car outside before entering the museum. She added the gunman “apparently fired rather quickly, went outside and left.”The three dead were two women and a man, all of them shot in the face or throat, said Ine Van Wymersch, spokeswoman for the prosecutor’s office.Van Wymersch said one suspect was detained after he drove away from the museum around the time of the attack. A second person being sought for questioning left the area on foot. Van Wymersch said security camera footage was being studied to try to identify the person.