An anti-terrorist exercise is held in Singapore's Velocity shopping mall on Nov. 15, 2019. The Singapore Police Force conducted the anti-terrorist exercise codenamed "Exercise Heartbeat" at Velocity shopping mall on Friday. (Photo by Then Chih Wey/Xinhua)

An anti-terrorist exercise is held in Singapore's Velocity shopping mall on Nov. 15, 2019. The Singapore Police Force conducted the anti-terrorist exercise codenamed "Exercise Heartbeat" at Velocity shopping mall on Friday. (Photo by Then Chih Wey/Xinhua)

An anti-terrorist exercise is held in Singapore's Velocity shopping mall on Nov. 15, 2019. The Singapore Police Force conducted the anti-terrorist exercise codenamed "Exercise Heartbeat" at Velocity shopping mall on Friday. (Photo by Then Chih Wey/Xinhua)

An anti-terrorist exercise is held in Singapore's Velocity shopping mall on Nov. 15, 2019. The Singapore Police Force conducted the anti-terrorist exercise codenamed "Exercise Heartbeat" at Velocity shopping mall on Friday. (Photo by Then Chih Wey/Xinhua)

An anti-terrorist exercise is held in Singapore's Velocity shopping mall on Nov. 15, 2019. The Singapore Police Force conducted the anti-terrorist exercise codenamed "Exercise Heartbeat" at Velocity shopping mall on Friday. (Photo by Then Chih Wey/Xinhua)