On May 12, 2018, six workers from Shanghai AIJINKE Engineering Construction Services Co. died on the spot of an explosion when they were maintaining a benzene tank at Shanghai SECCO Petrochemical Co. The incident was characterized as a disastrous incident caused by hot work in a confined space. This article aimed to analyze the incident in a chronological order by using the event sequence diagram. The FLACS software was used to simulate the variation of pressure and temperature over time when benzene vapor was ignited in the tank. Multilayer bow‐tie analysis was adopted to explore the causes of the explosion, along with the corresponding consequences, and preventive measures. The analyses show that the primary causes were the unsafe behaviors of on‐site workers, hazardous conditions of in‐tank substances, risky factors in the construction environment, and deficiencies in process safety management. Based on the qualitative and quantitative analyses, we emphasize three considerable reasons, which include inappropriate flammable gas detection before the operation, failing to test for flammable gases during the hot work, and deficiency of the Management of Change. Finally, the article concludes with a summary of lessons learned as well as suggestions for incident prevention and safety improvement.