Updated

A gunman in Austria killed four people, including three police officers, and fired sporadically at police on Tuesday after barricading himself in a farm building, police officials said.

After a 12-hour standoff, police stormed the building and were searching for the suspect, Interior Ministry spokesman Karl-Heinz Grundboeck told The Associated Press.  It wasn't immediately clear whether he was still in the building and the search was widening to other nearby buildings on the farm grounds.

The killings began shortly after midnight Monday when police stopped the man on a road near a wilderness area west of Vienna, where frequent poaching incidents occur.

The gunman fled in his car, which landed in a ditch in the nearby town of Annaberg, then shot and wounded a member of Austria's Cobra SWAT team at a police checkpoint, said Grundboeck.

An ambulance raced to the scene, but the gunman shot and killed its driver as he tried to give first aid to the wounded policeman, who later died.  The gunman also shot and wounded another officer at the scene.

Later Tuesday, another officer who had been missing was found shot dead in his patrol car, said Grundboeck. Regional police spokesman Roland Scherscher said that officer was apparently killed after the suspect carjacked the police vehicle and took him hostage.

The attacker then fatally shot a second police officer at a roadblock before barricading himself in the farm building on the outskirts of Melk, a central town 40 miles west of Vienna, Grundboeck said. The gunman sporadically fired at police units near the building.

Scherscher said he could not confirm an Austrian media report that the suspect was shot in the abdomen by police before he sought refuge inside the farm building.

State broadcaster ORF reported that the suspect was a 55-year-old poacher. Police identified him only as Alois H, in keeping with Austrian law that keeps criminal suspects anonymous .

The provincial government of Lower Austria ordered black flags flown from all public buildings in honor of the dead.