Manzo, 40, was shot on Saturday while attending a candlelight Day of the Dead festival in the city centre of Uruapan, in the violence-plagued western state of Michoacan.
Two suspects were arrested and a third was dead, Mexico’s security ministry said on Saturday.
Sheinbaum called an emergency meeting of her security cabinet on Sunday morning, later condemning Manzo’s “vile” assassination in a statement on X.
“We reaffirm our commitment to deploy all the State’s efforts to achieve peace and security with zero impunity and full justice,” Sheinbaum wrote.
A march was called for Sunday in Michoacan’s capital, Morelia, to demand justice for Manzo’s death and an end to violence and corruption.
One of the few independent politicians elected to office in Mexico, Manzo had been Uruapan’s mayor since September 2024. Since taking office, Manzo, often seen wearing a bulletproof vest, had called on the federal government to do more to fight organised crime while expressing fears for his own safety.
“I don’t want to be just another mayor on the list of those executed, those whose lives have been taken from them,” Manzo said in an interview in September with Mexican journalist Joaquin Lopez-Doriga.
Uruapan has been called Mexico’s avocado capital because it sits in the heart of Michoacan’s avocado-growing region. The industry has seen rapid growth due to booming US demand, making avocado production a target for organised criminal groups.
Multiple politicians, including other mayors, and journalists have been killed in recent months and years.
“How many mayors haven’t they killed because they opposed making these pacts with organised crime?,” Manzo asked in a September interview with Mexico’s Milenio TV.
He appealed to Sheinbaum for stronger public security measures and said Uruapan’s avocado industry gave it importance ahead of a coming review of Mexico’s trade deal with the US and Canada.
Manzo also said greater determination was needed on the part of security minister Omar Harfuch.
“Minister Omar Harfuch, help us,” Manzo said in the interview.
In a Sunday press conference, Harfuch said Manzo had had federal protection since December 2024, which was reinforced in May. The protection included 14 National Guard troops tasked with perimeter security, while local police provided immediate security.
“The aggressors took advantage of the vulnerability of a public event,” Harfuch said, referring to Manzo’s murder. “Be certain that there will be no impunity.”
US officials condemned the killing.
“The US stands ready to deepen security cooperation with Mexico to wipe out organised crime on both sides of the border,” Deputy secretary of state Christopher Landau wrote on X, sharing a photo of Manzo with his young son shortly before the mayor’s murder.