Since July, the Indonesian volcano Anak Krakatau has shown an increase in volcanic activity, and on December 22, an eruption followed by a tsunami confirmed the worst of the country’s fears.

At 7:30 PM MST, between the highly populated islands of Java and Sumatra, the Sunda Strait was struck by a deadly tsunami. The disaster agency of Indonesia says over 400 people died, more than 100 went missing, and about 40,000 were displaced. According to The Guardian, among the debris were over 600 homes, 60 shops, and 420 vessels–all demolished in the tsunami.

A two-minute eruption of Anak Krakatau the day prior and undersea landslides most likely caused the tsunami, the geological and weather service of Indonesia says. On December 29, Indonesia’s Centre of Volcanology and Geological Hazard Mitigation reported that Anak Krakatoa decreased in height after the eruption, going from 338m above sea level to 110m.

Scientists say that since a volcanic eruption set off the massive sea wave rather than an earthquake, a warning wasn’t triggered. The people of Indonesia were told by local experts that Anak Krakatau’s activity was low-scale for such a highly active volcano, so when the disaster hit, many were unprepared and confused. Sutopo Purwo Nugroho, the chief spokesman for the Indonesian disaster agency, said on Twitter that an early warning system specifically designed to detect tsunamis caused by volcanic activity or underwater landslides must be built.

The National Agency for Disaster Countermeasure (Indonesia’s board for natural disasters) released a report on December 27. According to this report, the Volcanical Survey of Indonesia recommended that anyone should not be within a 5 km radius of the crater peak since they could be “dangerously affected” by incandescent rocks, hot clouds, and thick volcanic ash.

Indonesian editor Rebecca Henschke for the global news network BBC has been with rescuers of those affected by the disaster, saying popular local tourist destinations and houses constructed of wood, bamboo, and tin roofs have completely been reduced to rubble, as have larger, more substantial buildings along the beaches. Many were trapped and killed in the falling of hotels, and that has been reflected in the death toll.

The Indonesian rock band Seventeen had been performing at an end-of-the-year party when they were swept off stage by a large wave, killing several of the band’s members. A video of this exact incident surfaced and went viral across social media.

Since the initial tsunami-triggering eruption, Anak Krakatau has continued to erupt almost daily, instilling in everyone the paranoia of returning to the coasts. Even if the islands were safe from any impending tsunamis, many people don’t have anything to come back to–the tsunami took their homes away from them. People have begun to rebuild their fallen houses and buildings, but for some it will take months and a significant amount of money to accomplish this.