A gang brought down a helicopter during a police operation in Mexico's troubled western state of Michoacan, killing the pilot and three officers, the governor said.
The aircraft was backing an operation to arrest leaders of criminal groups on Tuesday when the "official helicopter was downed" in an area with rough terrain, Governor Silvano Aureoles wrote on Twitter.
Another officer was injured in the crash.
Aureoles did not say how the helicopter was shot down in the region of Apatzingan, a city located in Tierra Caliente (Hot Land), a region that has been beset by drug violence and vigilante justice for years.
"In accordance to the responsibility to protect citizens, the state and federation won't give up in the fight against crime," the governor wrote.
It is the second time since 2015 that a gang downs a helicopter in Mexico. Last year, the Jalisco New Generation drug cartel in neighboring Jalisco state used a rocket launcher to hit a military helicopter, killing seven soldiers and policewoman aboard.