Nagasaki mayor assassinated during campaign

Article title: Nagasaki mayor assassinated during campaign
Source: Mainichi Weelkly(online)
Downloadedfrom:http://weekly.mainichi.co.jp/2007/04/nagasaki_mayor_assassinated_du_1.html on Monday, April 30

NAGASAKI ― Nagasaki Mayor Ito Itcho, who was seeking re-election, died on April 18 after being shot by a gangster in front of his campaign office a day earlier, police said.
Ito, 61, died at Nagasaki University Hospital at 2:28 a.m. from loss of blood.
Police arrested Shiroo Tetsuya, 59, a senior member of the Sui‐shin-kai, then affiliated with the Yamaguchi-gumi crime syndicate, and charged him with homicide. Police suspected that he was in a dispute with the municipal government and had a grudge against Ito.
Ito's predecessor, Motoshima Hitoshi, 85, who was seriously injured 17 years ago after being shot by a right-winger for his remarks that Emperor Showa was partially responsible for Japan's involvement in World War II, expressed anger over the incident.

“It's a shame that the two successive mayors of the city were shot," Motoshima said.

WHy two successive mayors in Nagasaki were shot?
Is there any particular chavacteristic in politics?