A Philippine mayor who paraded suspected drug dealers through the streets of his city, but also alleged to have drug ties himself, was shot dead while attending a weekly flag-raising ceremony.

Mayor Antonio Halili of Tanauan city in Batangas province south of Manila was shot in the chest by a still unknown-gunman on Monday and died on the way to a hospital.

A video of the assassination – posted on social media – showed Halili and civil servants outside the city hall singing the Philippine national anthem, when a sound of single gunshot rang through the crowd, followed by screaming as the ceremony was cut short.

Watch | Aktwal na video ilang segundo bago barilin si Tanauan Batangas Mayor Antonio Halili sa flag raising ceremony kaninang umaga.

? Gerry Yson Laresma pic.twitter.com/zm9z4v3ORH

— Jeff Caparas (@jeffcaparas) July 2, 2018

The bullet hit a mobile phone in Halili’s coat pocket then pierced his chest, police told AP news agency.

“We are shocked, we are saddened,” Vice Mayor Jhoanna Villamor, who was standing beside Halili, told radio station DZBB after the shooting.

Philippine police chief Oscar Albayalde said people in the crowd did not see anybody approach the mayor.

“They just heard a gunshot so the assumption or allegation was it could have been a sniper shot,” Albayalde said in a news conference, adding that an investigation was under way.

Police said they were scouring a nearby elevated grassy area, where the gunman may have fired the shot.

‘Walk of shame’

Halili became controversial two years ago when he ordered drug suspects to be paraded in public in his city, in a campaign that was dubbed “walk of shame”.

The suspects were forced to wear cardboard signs that read “I’m a pusher, don’t emulate me” in a campaign that alarmed human rights officials.

Police officials, however, also linked Halili to illegal drugs, an allegation he strongly denied. He said at the time that he would resign and would be willing to be publicly paraded as a drug suspect if police could come up with evidence to support the allegation.

Halili was stripped of his supervisory powers over local police in October 2017 due to a proliferation of illegal drugs in his city.

In an interview with Reuters news agency in August 2016 – the second month of the crackdown – he said he backed President Rodrigo Duterte’s campaign but believed drug kingpins should be the main targets, otherwise thousands of people would be killed.

He expressed concern over the way police conducted the war on drugs and the reliability of their intelligence, and that he might be accused of colluding with narcotics gangs.

“No one is safe – mayors, governors, congressmen – just a false intelligence report by the police can end up with any of them being destroyed,” he said in the interview.

Halili became controversial two years ago when he ordered drug suspects to be paraded in public in his city, in a campaign that was dubbed “walk of shame” [AP]

“I have a feeling they (police) are going after the small fry to frighten the people,” he said.

‘Police being taunted’

On Monday, Albayalde, the police chief, said investigators would try to determine if the killing was connected to Halili’s anti-drug campaign.

Halili’s unusual campaign drew attention at a time of growing alarm over the rising number of killings of drug suspects under Duterte.

Since Duterte took office in 2016, more than 4,200 drug suspects had been killed in clashes with police, alarming human rights groups, governments and UN rights watchdogs.

Opposition politicians and human rights groups, however, have reported much higher death tolls, although Duterte and his officials have questioned the accuracy of those reports.

Halili’s killing came a few weeks after a Catholic priest was shot and killed while preparing to celebrate Mass in a village chapel in the northern Nueva Ecija province.

Senator Panfilo Lacson, a former national police chief, urged the police to impose stricter firearms control in light of the killings.

“The Philippine National Police should feel challenged, if not taunted,” he said. “And they must immediately consider stricter firearms control strategies before similar killings could reach ubiquitous levels.”

Meanwhile, the Human Rights Watch (HRW) called for an “immediate and thorough investigation” by Philippine authorities.

“While we did not agree with Mayor Halili’s method of dealing with crime and illegal drugs in his city, his murder is condemnable,” Carlos Conde of HRW said in a statement to Al Jazeera.

“We reiterate our call for an end to the culture of impunity in the Philippines where thousands have been killed in extrajudicial killings,” he added.