One person was killed and three others injured Tuesday when an explosion authorities say may have been an “intentional detonation” tore through a California medical building. Sources cited by NBC4 said it appeared an explosive device was addressed to a specific person in the Aliso Viejo medical building in Orange County. The blast sparked panic in the area, with children at a nearby daycare center fleeing as bomb squad investigators and FBI agents responded to the scene. Orange County sheriff’s Commander Dave Sawyer later said any suggestion the blast was intentional was only preliminary. “We cannot say exclusively that this explosion was intentional,” he told reporters, adding that an announcement would be made once the cause is confirmed.