The Cambodian military said Friday it was closing its investigation into a shooting that occurred in a forest rife with illegal logging, concluding one of its own police officers killed a prominent environmentalist then took his own life.

Chut Wutty had been taking photographs in a forest where a Chinese company is building a hydropower dam, and he refused to stop when officer In Ratana asked him to, military police spokesman Kheng Tito said. The two men then started arguing and cursing each other, until In Ratana shot Chut Wutty with his AK-47 assault rifle.

"When he learned that Chut Wutty died, he killed himself with his own weapon," the spokesman said.

The death of Chut Wutty, the director of the National Resources Protection Group, had outraged human rights and environmental groups. A Cambodian rights group, the Center for Cambodian Civic Education, described it as "cold-blooded murder."

Illegal logging is rampant in Cambodia, and often occurs under the protection of government agencies or important persons, environmental groups have charged. In recent years, protests against land grabs by rich and influential people have often been suppressed by deadly force.

Patrick Alley, director of Global Witness, said the shooting exposed the risks environmental activists in Cambodia face "in the most shocking and tragic manner."

In Kong Chet, of the Cambodian human rights group Licadho, said the confrontation occurred when Chut Wutty refused to hand over a memory card containing photos taken in a protected forest notorious for illegal logging.

He said the activist had taken two journalists from The Cambodia Daily newspaper to see large-scale forest destruction and rosewood smuggling. The journalists were taken to a military police office for questioning, rights groups said.

Initially, Kheng Tito said the activist and officer had shot each other. But on Friday, he said a pistol with nine bullets was found inside Chut Wutty's car, but he did not shoot it and there was no exchange of fire.

Amnesty International said the journalists, Cambodian Phorn Bopha and Canadian Olesia Plokhii, were released later. It said Chut Wutty had received threats because of his activities, and called for "an immediate and proper investigation into what happened."

Global Witness' Alley said in a statement that Chut Wutty was "one of the few remaining Cambodian activists willing to speak out against the rapid escalation of illegal logging and land grabbing which is impoverishing ordinary Cambodians and destroying the country's rich natural heritage."