![A police officer role playing a suspect is attacked by a police dog during Tokyo 2020 and Tokyo Metropolitan Police Department Security Tests and Joint Drills ahead of the 2020 Olympics in Tokyo, Japan, September 28, 2018. (Photo/Agencies)](http://www.ecns.cn/hd/2018/09/29/09e6d963e69f4f6880a31090cd2ab50b.jpg)
A police officer role playing a suspect is attacked by a police dog during Tokyo 2020 and Tokyo Metropolitan Police Department Security Tests and Joint Drills ahead of the 2020 Olympics in Tokyo, Japan, September 28, 2018. (Photo/Agencies)
![A police officer role playing a suspect is attacked by a police dog during Tokyo 2020 and Tokyo Metropolitan Police Department Security Tests and Joint Drills ahead of the 2020 Olympics in Tokyo, Japan, September 28, 2018. (Photo/Agencies)](http://www.ecns.cn/hd/2018/09/29/9b66ee75bfd648b787eaab08b6134baf.jpg)
A police officer role playing a suspect is attacked by a police dog during Tokyo 2020 and Tokyo Metropolitan Police Department Security Tests and Joint Drills ahead of the 2020 Olympics in Tokyo, Japan, September 28, 2018. (Photo/Agencies)
![A police officer role playing a suspect (front) and security guards attend Tokyo 2020 and Tokyo Metropolitan Police Department Security Tests and Joint Drills ahead of the 2020 Olympics in Tokyo, Japan, September 28, 2018.(Photo/Agencies)](http://www.ecns.cn/hd/2018/09/29/e01a15b2d89c4d07b12f2a244af64fbf.jpg)
A police officer role playing a suspect (front) and security guards attend Tokyo 2020 and Tokyo Metropolitan Police Department Security Tests and Joint Drills ahead of the 2020 Olympics in Tokyo, Japan, September 28, 2018.(Photo/Agencies)
![A police officer role playing a suspect is attacked by a police dog during Tokyo 2020 and Tokyo Metropolitan Police Department Security Tests and Joint Drills ahead of the 2020 Olympics in Tokyo, Japan, September 28, 2018. (Photo/Agencies)](http://www.ecns.cn/hd/2018/09/29/fe2c764fb530426e8a71e2a17abde4cd.jpg)
A police officer role playing a suspect is attacked by a police dog during Tokyo 2020 and Tokyo Metropolitan Police Department Security Tests and Joint Drills ahead of the 2020 Olympics in Tokyo, Japan, September 28, 2018. (Photo/Agencies)