A tsunami warning was sent out - lasting just over 30 minutes - but it appears to have drastically underestimated the scale of the tsunami that would follow. So what went wrong?
A 7.5 magnitude earthquake occurred just off the island of Sulawesi at 18:03 local time (10:03 GMT) on Friday, triggering dozens of aftershocks.
Indonesia's meteorological and geophysics agency BMKG issued a tsunami warning just after the initial quake, warning of potential waves of 0.5 to three metres.
But it lifted the warning just over 30 minutes later.
Palu - a city in Sulawesi located in a narrow bay - was hit by waves as high as six metres. The surging water brought buildings down and caused widespread destruction. Hundreds of people had gathered for a beachfront festival and it was was a scene of horror as waves powered over the beach - sweeping up everything in their path.
Indonesia's National Disaster and Mitigation Agency has said that most of the victims in Palu were killed as a result of the tsunami.
Many critics have accused BMKG of lifting the warning too early, though the agency says the waves hit while the warning was still in force.
BMKG chairwoman Dwikorita Karnawati told the Jakarta Post that the decision to end the warning was made after the agency received information about the tsunami, including a field observation made by a BMKG employee in Palu.
She added that the tsunami alert ended at 18:37, minutes after the third and last wave hit land. She also said that there were no more tsunami waves after the alert ended.