MANILA - (3rd UPDATE) Tanauan Mayor Antonio Halili of Batangas, who was known for ordering suspected criminals to take "walks of shame", was shot dead during a flag ceremony in his city on Monday, police confirmed.

Halili and other city hall officials and employees were singing the national anthem at Tanauan City Hall when a gunshot rang out, causing panic, a video from the local information office showed.

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People scream in panic after a gunshot interrupts the flag raising ceremony at the Tanauan city hall. Video courtesy of the Tanauan information office

Police said an unidentified gunman shot Halili in the chest. The mayor was declared dead on arrival at the CP Reyes Medical Center, according to Calabarzon police director Chief Supt. Edward Carranza.

BREAKING: Tanauan City Mayor Tony Halili, pumanaw na matapos mabaril sa flag ceremony. pic.twitter.com/uPXLXalVut

— DZMM TeleRadyo (@DZMMTeleRadyo) July 2, 2018

The gunman may have been positioned in some bushes 150 meters away from the city hall, said Carranza.

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Police sealed off all exit points in the village and formed a special investigative task group in search for the killer.

Malacañang denounced Halili's killing and promised to bring the gunman to justice.

"Kinokendena po natin itong pagpatay kay Mayor Halili... Sa pamilya at sa mga constituents ni Mayor Halili, bibigyan natin sila ng katarungan. Iimbestigahan, lilitisin ang mga tao na nasa likod ng pagpatay kay mayor," Presidential Spokesperson Harry Roque told reporters.

(We condemn the killing of Mayor Halili. We will give justice to the family and constituents of Mayor Halili. We will investigate and try the people behind the mayor's killing.)

Presidential Spokesperson Harry Roque, kinondena ang pamamaslang kay Mayor Antonio Halili ng Tanauan City; tiniyak ang hustisya sa pamilya | via @dzmmRP45 pic.twitter.com/dVLTpr1Rgp

— DZMM TeleRadyo (@DZMMTeleRadyo) July 2, 2018

Halili made headlines in 2016 when he paraded suspected drug criminals in public.

• 11 drug suspects take walk of shame in Batangas
• Duterte backs mayor who parades crime suspects

He, however, was included on the list of high-value drug targets of the police and subjected to "Oplan Tokhang." Halili had denied the allegation that he was involved in narcotics.

In 2017, he lost supervision over the police, along with other officials accused of dabbling with the narcotics trade.

• 'Duterte ng Batangas,' tinarget ng Tokhang

With reports from Fay Virrey and Noel Alamar, ABS-CBN News