Senior Police Officer 1 Rafael Albero Jr., investigator of the Ronda police station, quoted two witnesses, Archel Gaging and Jeffrey Mario, who said that the armed men on board a white van arrived at the two-story Ronda municipal hall at about 1:30 a.m. and went straight to the mayor's office.
"After a second, a burst of fire was heard from the mayor's office and then after, the unidentified persons left", said Tagupa.
Blanco, who ran for mayor under the Liberal Party in 2010, was one of two mayors in Cebu said to be closely watched by the Philippine National Police (PNP) on suspicion of being involved in drug operations.
Blanco had reportedly been staying at the municipal hall even before he was tag as an alleged narco-politician by Duterte in 2016.
CITY-The mayor of Ronda town insouthern Cebu was gunned down inside his office early Wednesday morning.
Some of those killed have been linked to the drugs trade or crackdowns upon it.
Under the terms of this order, Blanco could not choose the town's chief of police, inspect police personnel or exercise any other functions related to the local police. In July, staunchly anti-drug Antonio Halili, the mayor of Tanauan City, was killed by a sniper during a flag-raising ceremony.
The mayor was pronounced dead at the hospital and the motive for the killing is under investigation.
Six months before his death, Blanco's nephew and vice mayor Jonah John Ungab was shot dead by unidentified assailants after attending a hearing at the Cebu City Palace of Justice.
Ungab, a lawyer, served as legal counsel to self-confessed drug lord, Kerwin Espinosa.
At the time, police spokesman Risty Sibay explained Duterte had received "intelligence reports" implicating Blanco in the drug trade, and noted that only the president could return his authority over local law enforcement.
Mr Blanco and Mr Halili are among at least six mayors or vice-mayors killed in the Philippines since May.
Duterte and the police have denied a policy of condoning illegal killings and cite the deaths of many policemen in clashes as proof of the danger posed by drug suspects.