As Batik Air Flight 6231 readied for takeoff, the ground began to violently shake in Palu, a city on the eastern Indonesian island of Sulawesi.
In the wobbling air traffic control tower, as other personnel fled, Anthonius Gunawan Agung, 21, stayed put, helping guide the pilot down the runway. Moments after the plane went airborne, the earthquake intensified, and Mr. Agung leapt out of the tower to his death as its roof collapsed.
“We have found corpses from the earthquake as well as bodies swept up by the tsunami,” Sutopo Purwo Nugroho, a spokesman for the Indonesian disaster agency, said in a television interview.
Indonesian officials were preparing for a sharp rise in the death toll because search-and-rescue teams had yet to reach populous coastal settlements near Palu. Vice President Jusuf Kalla of Indonesia told a local news website that thousands may have died, with an unknown number washed out to sea.
The tsunami inundated Palu just as preparations were underway for a beachside festival with dances and other performances, and the festival’s security personnel are believed to be among the victims.
Although Indonesia is chronically at risk of tsunamis, Andri Manganti, a resident of Palu who lost his home in Friday’s earthquake, said that no warning siren sounded before the tidal wave — estimated to be a towering 18 feet high — struck the city of about 300,000 people.
Mr. Sutopo said on Saturday that as he was preparing information to alert the public about the tsunami threat, the warning was abruptly halted by the geophysics agency.
Video clips taken along a bustling seaside avenue in Palu appear to show two successive waves, battering the coast within a few minutes of each other.
Another video, taken just down the road, shows the second wave crashing over the roofs of one-story buildings, which then disappear beneath the turbulent water. The water surged around a mosque, whose large green dome had already collapsed, probably from the quake.
On Saturday afternoon, Mr. Sutopo said that in addition to the 405 people confirmed dead in Palu, 540 people were injured and 29 were missing. About 2.4 million people are believed to have been affected by the earthquake, according to Indonesia’s central statistics agency.
Mr. Manganti’s aunt and cousin, who lived by the coast, are among those yet to be found. His sister, Lidia Manganti, who lives in Jakarta, has been frantically trying to reach her relatives over phone lines that are working only sporadically.
