Witnesses saw no sign of trouble before a young man left his friends in a sushi shop and was shot dead in the carpark of a busy Brisbane shopping centre.

The 22-year-old was reportedly shot in the head after dining with friends at a restaurant at Warrigal Square Shopping Centre at Eight Mile Plains about 7.15pm (AEST) on Thursday.

He died later in Princess Alexandra Hospital.

A diner at a nearby restaurant says a supermarket trolley pusher raised the alarm.

"(He) came in, asked the guy behind the counter could he please ring the ambulance and police, urgent. Someone had just been shot in the carpark," the man told the Nine Network.

A triple-zero operator told the owner of the restaurant to check on the victim.

"They want me to go near to the victim and see what's happening," the restaurant owner said.

"He was lying on the floor, blood all over the face."

The shooting occurred less than 24 hours after a fatal shooting in the nearby suburb of Rochedale South, but police have no indication the two attacks were linked.

On Wednesday night, John Lazzaro, 56, was gunned down in his loungeroom by two masked men as his 19-year-old daughter looked on.

Police Commissioner Bob Atkinson said Thursday's shooting at Eight Mile Plains was clearly deliberate.

"We believe this is not a random drive-by shooting," Mr Atkinson told reporters.

"The indications so far show this was deliberate, intentional and focused."

Detective Superintendent Michael Niland said the victim was known to police.

"We do not believe this is gang-related at this stage, but of course we keep an open mind," Det Supt Niland said.

He said several witnesses were assisting the investigation and police were talking to the victim's family.

Police are seeking information on a two-door silver BMW seen on CCTV footage which may be linked to the shooting.

Det Supt Niland said the car had a sun roof and was believed to be a 2001 model.

Witnesses say the victim was a young Asian man who had dined at a sushi restaurant before the shooting.

The owner of the sushi restaurant, Naoki Yamamoto, said there had been no sign of trouble before the young man left after receiving a phone call.

"He was just sitting quietly talking to his friends and eating sushi," Mr Yamamoto told AAP.

"Then he had a phone call and walked outside to the car park and never came back in.

"I didn't see the shooting itself. My restaurant was very, very busy last night, and I was busy making sushi."

Shop owners returning to work on Friday morning were still in shock.

Bakery owner Jessica told ABC Radio such violence was not common in the area.

"We are all pretty shocked and amazed this morning," she said.

Police were interviewing a number of witnesses and not allowing people to take their vehicles from the carpark until crime scene investigations were completed.