MEXICO CITY, Mexico (CNN) -- A mayor in Mexican President Felipe Calderon's home state was ambushed and killed by a group of heavily armed men as he returned to his house, news reports said.
It was the second assassination attempt in eight days on Vista Hermosa Mayor Octavio Manuel Carrillo Castellanos, the Cambio de Michoacan newspaper said on its Web site Wednesday.
Carillo was pulling up to his home around 6 p.m. Tuesday when at least two men got out of a vehicle and opened fire. There were conflicting reports over whether a second vehicle with armed men may have been involved.
Family and others came to Carillo's aid while a police officer stationed at his house called for help, Cambio de Michoacan said.
Carillo was taken to a nearby hospital, where he died around 7:20 p.m..
Officials said they did not have a motive or know if the mayor had received any threats.
But El Excelsior newspaper reported that investigators are looking into Carillo's recent firing of a Vista Hermosa police commander and an officer.
Carillo, who took office on January 1, 2008, was the second mayor in the Pacific coast state of Michoacan killed in the last eight months. Marcelo Ibarra Villa, the mayor of Villa Madero, was ambushed in June while riding in his truck with his wife, El Excelsior said.
The gunmen escaped in both instances.
Tuesday's killing came on Mexican Flag Day, just hours after Calderon vowed that his government would continue to battle the drug cartels that have ravaged the country.
The mayor's death also came four days after the sudden resignation of the police chief in Ciudad Juarez, across the border from El Paso, Texas. Police Chief Roberto Orduna had received death threats from local drug cartels and resigned after the recent deaths of eight police officers under his command.
Violent deaths reached record levels in Mexico last year as drug cartels battle each other and the Mexican government. More than 5,400 killings were reported in 2008, more than double the tally in 2007. Authorities and analysts said a new record could be set this year.
Narcotraffickers have adopted a campaign of intimidation against authorities, and the deaths of police, mayors and other officials have become common.
Last year, more than 100 police were killed in Ciudad Juarez in attacks blamed on organized crime.
"They started killing police officers when they were going home or getting into police cars," Mayor Jose Reyes Ferriz told reporters last week.
Just last week, the city's police director of operations was gunned down in his car. Another police officer and a prison guard were found dead Friday morning.
On Friday, the U.S. State Department renewed a travel alert for Americans considering a visit to Mexico.
"The situation in Ciudad Juarez is of special concern," the alert said. "Mexican authorities report that more than 1,800 people have been killed in the city since January 2008. Additionally, this city of 1.6 million people experienced more than 17,000 car thefts and 1,650 carjackings in 2008."
In addition, the University of Arizona warned its students against going to Mexico on spring break this year, and Arizona State University is considering the same advisory.
"These are flat-out organized crime groups like we think of any other organized crime groups. They are not a small gang on the corner. These are large organizations," said David Denlinger, chief of the Arizona Department of Public Safety.