A man who allegedly killed a colleague at an Australian grain silo Thursday was in a critical condition after turning the gun on himself, police said.

The 25-year-old allegedly shot a man in his 40s at the silo in the town of Kellerberrin at about 8.40 a.m. and then fled the area, the Western Australia Police Force said.

The police force issued an active shooter alert to warn members of the public to remain indoors as a search for the suspect got under way.

The gunman was believed to be armed, dressed in camouflage clothing and on the move north of the town, about 125 miles east of Perth, the Western Australia state capital, police said.

A suspect was eventually located in a farm paddock about 12 miles from Kellerberrin, Western Australian Police Regional Commander Rod Wilde said. He was airlifted to a hospital with serious injuries, Wilde said.

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"Police were negotiating. There ... had been talking to him for several hours," the commander told reporters.

Wilde said the suspect and his alleged victim had worked together for several years.

"Obviously it’s a tragic outcome for everyone involved," he said.

The homicide squad is investigating the older man's death.

Shire of Kellerberrin chief executive Raymond Griffiths said both men were local residents and the community of about 950 people was devastated by the events.

"Kellerberrin is a tight-knit community ... We are all in shock," Griffiths said in a statement. "Our focus in the coming days will be providing any support the families that have been impacted might need."

Griffiths thanked police for their "quick response" and asked for the privacy of the victim’s family and the community to be respected.