A woman is dead after being shot in the head at a McDonald's restaurant at Helensvale on the Gold Coast.

The 49-year-old was shot by a 57-year-old man, who then turned the gun on himself, in the dining area of the restaurant on Siganto Drive about 9:15am on Thursday.

Queensland Police Services' Detective Inspector Mark White said the man was taken to Gold Coast University Hospital with critical head injuries.

The man and woman were known to each other and were both from Maryborough on the Fraser Coast.

No-one else was physically injured.

"I am not going to go into the specifics of it because it is quite a graphic and tragic incident that has occurred and that is obviously the focus of our investigation," he said.

"We're also looking at the CCTV footage that was available inside the premises."

He said police were still in the process of verifying the identities of the man and the woman.

"Obviously we have to show some respect to the family in this regard as well," he said.

He said police did not know how many people were inside the restaurant at the time, but said the witnesses were customers, not staff.

"Absolutely only imagine what it's like to go about your normal business and to have something like that occur right in front of you," he said.

"We are mindful of that and we are looking at avenues to ensure that any person who did witness it or was nearby can access some form of counselling or support that they may need.

"Some of them are actually quite distraught to be honest, and when you have an appreciation of what's occurred, you can understand that.

"Part of the process that we're going through with taking statements — and we appreciate their cooperation — is to also ensure if they do need some support, that we can make appropriate referrals or get in touch with people, because it's not something that you would encounter in your everyday life."

Police seal off the entrance to the McDonald's restaurant at Helensvale. ( Supplied: Queensland Police Service )

'He's got a gun, we better step back'

A man who witnessed the fatal shooting has described the moment the man walked up to the woman in the restaurant and put his arm around her before shooting her.

The man, who did not want to be named, said he was about to go into the restaurant when he saw the couple struggling in their car.

"Then she got out ... she came inside. He sat in the car for maybe a minute then he got out and his expression didn't change for a moment," the man said.

Sorry, this video has expired Police discuss shooting at Gold Coast McDonald's

"He just walked inside. He sort of showed the gun he had in his hand and I said to the guy that was next to me 'he's got a gun, we better step back' and he just walked inside, put his arm around her and just put the gun to her chest and shot her. It was just horrific."

"And then he just did the same, he just put the gun to his own head and collapsed over the top of her.

"She yelled out [that] he was trying to kill her before she ran inside but that was about ... I don't think he said anything.

"It's quite amazing how you could be just walking into a little restaurant like that and something like that just happens. The whole thing was just a minute, minute-and-a-half.

"When he fell over the woman's body, I thought he still had the gun in his hand because I didn't see the gun anywhere else and someone started to approach and he was convulsively breathing.

"And I said 'Don't go near him because he's still got the gun'."

Police declared an emergency situation at the McDonald's on Siganto Drive. ( AAP: Dave Hunt )

McDonald's workers 'all shocked up and terrified'

Detective Inspector White said the man had followed the woman into the restaurant.

"We do know that the male and female concerned were known to each other and that is all I can disclose at this point," he said.

"The female concerned had just walked inside to the premises.

Police said the shooting came after a woman walked into the McDonald's and a man followed her. ( AAP: Dave Hunt )

"The male person has come in into the premises as well and that's when the incident took place."

A statement from a McDonald's spokesperson said the company was assisting police.

"This is obviously a tragic incident and our thoughts are with the families," the statement said.

"We are caring for our employees and providing counselling services."

Hine Paki was nearby when the shootings happened and said the restaurant staff were visibly shaken.

"I've only seen the workers come out all shocked up and terrified," she said.