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MANILA (3rd UPDATE) - The mayor of Sudipen town in La Union was shot dead by unidentified assailants on Monday night, a police official told ABS-CBN News.

According to Bangar Police Chief Insp. Cirilo Butigan, Mayor Alexander Buquing and his wife, Vice Mayor Wendy Buquing, were on their way home when the assailants waylaid their vehicle in Barangay Cadapli.

Alexander was rushed to a hospital, but was declared dead on arrival.

According to staff members of Ilocos Sur District Hospital, the mayor sustained multiple gunshot wounds to the different parts of his body.

The mayor's driver, Bonifacio Depdepen, and his bodyguard, Rolando Juan Be, were also killed.

Wendy is still in the hospital for medical treatment.

Senior Supt. Ricky Layug, director of La Union Provincial Police Office, said the vice mayor is now out of harm's way.

Motive behind the ambush is still unclear, according to police investigators.

A special investigation task group will be formed to probe the incident.

• Mayors and Vice Mayors killed under Duterte administration

Alexander is the 17th elected official killed during the Duterte administration.

Below is a list of mayors and vice mayors killed under Duterte's administration.

1. Vice Mayor Aaron Sampaga of Pamplona town, Cagayan - August 5, 2016

2. Mayor Samsudin Dimaukom of Datu Saudi Ampatuan town, Maguindanao - October 28, 2016

3. Mayor Rolando Espinosa of Albuera town, Leyte - November 5, 2016

4. Vice Mayor Anwar Sindatuk of Datu Saudi-Ampatuan town, Maguindanao - November 27, 2016

5. Mayor Mohammad Limbona of Pantar town, Lanao del Norte - December 30, 2016

6. Mayor Arsenio Agustin of Marcos town, Ilocos Norte - June 3, 2017

7. Mayor Joven Hidalgo of Balete town, Batangas - June 10, 2017

8. Mayor Reynaldo Parojinog of Ozamiz City, Misamis Occidental - July 30, 2017

9. Vice Mayor Jackson Dy of Roxas town, Oriental Mindoro - September 23, 2017

10. Vice Mayor Jonah John Ungab of Ronda town, Cebu - February 19, 2018

11. Mayor Ronald Tirol of Buenavista town, Bohol - May 27, 2018

12. Mayor Antonio Halili of Tanauan City, Batangas - July 2, 2018

13. Mayor Ferdinand Bote of General Tinio town, Nueva Ecija - July 3, 2018

14. Vice Mayor Alex Lubigan of Trece Martires town, Cavite - July 7, 2018

15. Vice Mayor Al-Rashid Mohammad Ali of Sapa-Sapa town, Tawi-Tawi - July 11, 2018

16. Mayor Mariano Blanco III of Ronda town, Cebu - September 5, 2018

17. Mayor Alexander Buquing of Sudipen, La Union - October 1, 2018

- with reports from Justin Aguilar, ABS-CBN News