By CHRISTOPHER SHERMAN and E. EDUARDO CASTILLO for the Associated Press

MEXICO CITY (AP) — Heavily armed gunmen attacked and wounded Mexico City’s police chief in a brazen operation that left three people dead, Mayor Claudia Sheinbaum said Friday. The chief later tweeted, apparently from the hospital where he was being treated, that the Jalisco New Generation cartel was responsible.

Sheinbaum said in a news conference that the police chief, Security Secretary Omar García Harfuch, was being treated in a hospital, but was out of danger.

She said a 3 1/2 ton truck holding gunmen with rifles blocked the chief’s SUV and opened fire.

Two of those killed were part of García’s security detail. The third was a woman who just happened to be driving by. Sheinbaum said that the city’s security cameras recorded the attack.

“This morning we were attacked in a cowardly way by the CJNG,” García tweeted, using the Spanish-language acronym for the Jalisco New Generation Cartel, Mexico’s most violent criminal group.

“Two colleagues and friends of mine lost their lives,” García wrote. “I have three bullet wounds and various pieces of shrapnel. Our nation has to continue standing up to cowardly organized crime. We will continue working.”

A federal official who was not authorized to speak publicly confirmed that it was García’s Twitter account.

The Jalisco New Generation cartel has been behind brazen attacks before, including the downing of a military helicopter. The cartel traffics in drugs and operates extortion rackets and other criminal enterprises.

Asked about the tweet from García, Sheinbaum declined to speculate on who was responsible.

Mexico City Attorney General Ernestina Godoy Ramos said on Twitter that there were 12 arrests and that her office was investigating the attack.

The police said in a statement that gunmen armed with .50 caliber sniper rifles and grenades exchanged fire with the chief’s security detail. The statement said two police were wounded. Harfuch was hospitalized in stable condition, it said.

The attack occurred around 6:30 a.m. on Mexico City’s grand boulevard Paseo de la Reforma in an area of large homes surrounded by walls and foreign embassies. Photographs from the scene showed a bullet-riddled black SUV and a high-sided construction truck with a number of rifles in the back that apparently hid the gunmen until the ambush.

There was no immediate word on motive or the identity of the attackers, but a number of organized crime groups operate in the city.

President Andrés Manuel López Obrador offered his support and solidarity to Sheinbaum and the city’s public security forces.

“It has to do without a doubt with the work he is carrying out to guarantee peace and tranquility,” López Obrador said.

Mexico’s federal Security Secretary Alfonso Durazo, who was travelling with the president, condemned what he called a “cowardly” attack. “It’s clear that the work of the (police) is touching strong criminal interests,” he tweeted.

Earlier this month, a federal judge and his wife were killed at their home by gunmen in the western state of Colima. The judge had handled a number of cases related to organized crime.