Man who killed Queensland cop has been shot dead after a 21-hour standoff with police.

A gunman who shot dead Queensland policeman Brett Forte has himself been killed during a final shootout with police west of Brisbane.

Police say Rick Maddison ran from the shed he had been holed up in on a rural property at Seventeen Mile in the Lockyer Valley and fired at heavily-armed police on Tuesday.

Special Emergency Response Team (SERT) officers shot back and Southern Region Assistant Commissioner Tony Wright confirmed Maddison was declared dead at the scene.

“The male person who is the subject of our inquiries in relation to the death of Senior Constable Brett Forte has exited the building in which he was in,” said Mr Wright.

“He has been challenged by police.

“At that point in time, he has fired at those police. Specialist police have returned fire. The male person has been shot and that male person has been declared deceased at the scene.”

Locals say they heard four shots at the end of a tense 21-hour siege, which occurred in Maddison’s property on the top of a ridge.

Residents also said the 40-year-old had a wide collection of firearms, including machine guns, and heard him shooting at the property most days.

A member of the Toowoomba’s Tactical Crime Squad, Sen Const Forte’s death came after police tried to pull over Maddison on Monday afternoon.

Maddison – previously charged with torture among other offences – gunned down Sen Const Forte without warning.

“I know was it was completely unexpected and Brett sadly never had a chance,” Queensland Police Union chief executive Ian Leavers said.

He was tracked by police to the shed around 4pm on Monday after he also fired at other officers, police vehicles and a police helicopter.

Maddison has been described in media reports as a career criminal, which included a 2008 arrest in Gatton for torture, deprivation of liberty, and drug offences.

“This guy they are after, he has got serious history,” Mr Leavers said, without going into details.

“I know a bit about him but while it is unfolding I have to hold back.”

Mr Leavers indicated Maddison should not have been at large.

“The 60,000 police in Australia, are hurting today,” he said.

Queensland Commissioner Ian Stewart paid tribute to Sen Const Forte as a “fine son” of the police service.

Shadow police minister Tim Mander joined Premier Annastacia Palaszczuk in paying tribute to Sen Const Forte, whose wife Susan is also a police officer.

“This is a stark reminder that our police officers, every day, literally, put their life on the line to protect us from mongrels like this,” Mr Mander said.

Police cordoned off a large section of Seventeen Mile, forcing some locals to sleep in their cars.

Local resident Megan Poole said she fled her Alvisio Rd home just after 3pm on Monday after hearing “machine gun fire” and seeing undercover police cars speed past.

“I don’t think I’ll ever forget that noise,” she said on Tuesday.

Mourners have been laying floral tributes for Sen Const Forte outside the Toowoomba police station and have been seen stopping officers in the streets to convey their condolences.