The most important task in case of the Nov. 26 election-eve shooting that caused one death and injured a former vice president's son is to find out whether there is a mastermind behind the incident, the minister of the interior said Friday. The investigation should focus on determining 'whether there is an individual mastermind or a ring behind the perpetrator, ' since prosecutors have obtained concrete evidence on the shooting thanks to the arrest of the assailant on the spot and the seizing of the murder weapon, Jiang Yi-huah told reporters. Asked whether there is a deadline for solving the case, Jiang said there is no deadline, but spelled out the government's hope that investigators will uncover the truth as soon as possible. Sean Lien, the son of former Vice President Lien Chan, was shot in the face while stumping for a city councilor candidate during a campaign rally in Xinbei City on the eve of the municipal elections. Lien is in stable condition at National Taiwan University Hospital (NTUH) , but a bystander who was also shot in the head died of injuries soon after the incident. NTUH said Friday that Lien is recovering and that his facial nerves are functioning normally. The gunman's bullet pierced the left side of Lien's face and exited near his right temple, causing fractures of his cheekbones and two open wounds. The shooting had a great impact on the fairness of the elections and on social order, Jiang said, pledging reinforced efforts to prevent possible election- related violence in the future. 