Former Rebels boss gunned down at Perth Motorplex, 5yo boy receives minor wounds

The 51-year-old was gunned down in front of hundreds of innocent bystanders during a race at the venue at about 8.40pm.

A 31-year-old patched member of the Rebels and the five-year-old boy were sitting in close proximity to Martin, with both sustaining injuries during the shooting.

Police officers swarmed to the Motorplex following the gun shots, with St. John Ambulance treating the injured.

Gang Crime Squad officers are currently investigating the incident.

WA Police commissioner Chris Dawson said officers are at a "heightened state of readiness to ensure there are no retaliatory attacks."

"We will be relentless in our policing outlaw motorcycle gangs," he told reporters at a press conference on Sunday morning.

"Any bikie can guarantee they're going to get a lot more (police) contact. They already are all under significant police pressure and that pressure will ramp right up.

"The community is justifiably outraged at this type of violent criminal behaviour. This is not the Western Australia we want to live in."

Police are now calling on anyone with information or anyone who witnessed the event to come forward.

"We've got an extensive investigation underway," Commissioner Dawson said.

"I would ask anyone that has any mobile vision, contact us on Crime Stoppers."

Anyone with information or vision of the incident can contact Crime Stoppers on 1800 333 000 or make a report online at crimestopperswa.com.au