Two gunmen shoved their way into a radio studio and opened fire on a local activist, killing him while he was broadcasting, prosecutors in the Mexican state of Sinaloa said. It was the first on-air killing in recent memory in Mexico.

Listeners heard the gunshot that killed Atilano Roman Tirado, who had a weekly radio program as well as leading a group of farm families displaced by a dam.

"On air you could hear when the shot is fired, and then one of the co-workers is heard saying, 'Oh no, he killed him, he killed him,'" station director Sergio Ontiveros said Monday.

"That is when the transmission cut off ... The station operator dove to the floor and kicked out the master" cable, Ontiveros said.

The Fiesta Mexicana station in the Pacific coast city of Mazatlan was off air for about a half hour, and was operated remotely over the weekend before resuming normal operations on Monday morning.

Roman Tirado was a leader of about 800 families demanding compensation for being displaced by the Picachos dam.

In past years, the movement had staged blockades and protest marches, which had resulted in some arrests. Ontiveros said Roman Tirado focused on the land dispute and other news in his program, "Asi es mi Tierra" — roughly "That's how my land is."

"He was militant in his commentaries, he was critical, very critical," Ontiveros noted. "His situation almost demanded that of him."

Sinaloa state prosecutors said two men walked into the station Saturday and asked for Roman Tirado. One of the men waited outside the studio where Roman Tirado was broadcasting while the other walked into the studio and shot him.

"They violently forced their way in," Ontiveros said. "They asked for Atilano. The receptionist said he was there and said if they waited, she would tell him they wanted to see him," Ontiveros said. "But they pushed open the door and forced their way in to the studios."

The assailants hit another employee with the butt of a pistol, then shot Roman Tirado in the head and in the chest with a 9 mm pistol. He died later at a local hospital.

Sinaloa Gov. Mario Lopez Valdez said that the killing would not go unpunished, but officials had reported no arrests on Monday. State prosecutor Marco Antonio Higuera said the station offices did not have security cameras that might have recorded the killing.

Roman Tirado's movement had become somewhat less active over the last couple of years, and he had ventured into other lines of business. But, at its height, the movement had reported receiving telephone death threats against its leaders. In an article from 2010 posted on the movement's web site, a female leader said she had received a telephone call saying orders had been issued to kill her, Roman Tirado and two other leaders. It was not clear who made the threat.

The government gave houses to people whose villages were flooded by the construction of the Picachos dam, which started in 2006. However, the dwellings were tiny, shack-like structures.

Attacks on radio stations are rare in Mexico, though print journalists and photographers have frequently been the victims of attacks and killings.

According to the New York-based Committee to Protect Journalists, 75 journalists and media workers have been killed since 1992; the vast majority worked as reporters or editors for print media.

Ontiveros, who is also the director of the Sol de Mazatlan newspaper that shares a building with Fiesta Mexicana, said "as a media organization, we are demanding an end to this type of violence, these types of attacks, that threaten our safety as journalists.