A woman was shot dead in her car in front of two young teenagers after pulling into a property in North Queensland in an “absolutely shocking” attack that triggered a public lockdown.

A 66-year-old man who came to the 34-year-old woman’s aid was also fired at and hit in the chest. He was taken to hospital in a serious but stable condition.

Police said the woman had driven into Robb Place, in South Mackay, on Wednesday afternoon when a 31-year-old man approached and fired into the vehicle, striking the woman.

Seven News reports she was shot in the head.

Two terrified young teenagers who were also in the vehicle fled to a nearby residence, after which the 66-year-old man came to the woman’s aid, District Superintendent Graeme Paine said.

Police ordered an emergency declaration, placing numerous streets under lockdown at 5.20pm. Residents were told to stay indoors and avoid the area.

Patrols later found a suspect vehicle during a three-hour search.

About 7.45pm police arrested the 31-year-old man outside a fast-food restaurant and service station about two kilometres away from the scene of the shooting.

He was assisting police on Wednesday night.

The street in South Mackay where the woman had pulled into a property. Photo: 7NEWS

“I don’t have any details at this stage in relation to any sort of motive or reasons behind what’s occurred,” Paine said.

“The investigation is in its early stages but we are running out a number of different inquiries.”

Police did not know if the woman and two men were known to each other, but believed they “resided in close proximity to each other”.

Paine said police were examining multiple scenes.

He said the shootings were “an absolutely shocking thing” for the teens to have experienced.

“They obviously were very fearful and they’ve gone and sought help and that help was provided and unfortunately that male who also provided help has been injured, so an absolutely tragic situation,” Paine said.

“We don’t know exactly what’s happened obviously from the time the incident’s occurred to the time police arrived.

“There is a fairly short period,” Paine said.

Police issued a public safety emergency declaration. Photo: 7NEWS

A mechanic who pulled into the BP and witnessed the suspect’s arrest described the dramatic scene.

“I heard the brakes of one of the cop cars go off and I thought that’s a bit weird so I turned around and saw about four, five, six cop cars pull up at the same time,’’ Tyler Camilleri told The Courier Mail.

“They all get out and they are all screaming ‘Put the gun down, you’re under arrest, stop’ – you know, all that kind of stuff.’’

“He seemed to have put it down pretty quickly the moment he saw all the coppers.’’

Camilleri said his mother had told him to “stay away from South Mackay” because police were searching for someone.

“And then boom all this happened. Mum’s not going to like that.”

The emergency declaration was revoked late on Wednesday around Robb Place and Paradise, Archibald, Kindermar and Denton streets.

–with AAP