Now police have confirmed the attack follows a separate incident at a Southern River mosque on Saturday, in which a pig's head was left near the main entrance along with similar graffiti.
During a media conference, in which police released CCTV footage of three men wearing hoodies in the Thornlie area, Inspector Tony Jeavons said investigations were focused on determining if the attacks were linked.
"It's very disappointing that individuals in the community would commit these criminal acts," he said.
"At this stage investigations are trying to determine whether those two incidents are linked, but I'd like to reassure the West Australian community and particularly the Islamic community that police take these matters very seriously."
It was confirmed that four vehicles - a Toyota Prado, a Honda Legend, a Volkswagen Passat and a Toyota Corolla - were all damaged in Tuesday night's attack.
The Prado was gutted by the fire, which the Department of Fire and Emergency Services was required to extinguish before it spread to other vehicles.
Police also released footage from Saturday of a Nissan Navara driving around a Southern River mosque carpark.
It's believed Saturday's incident happened sometime between 7:30pm and 8:30pm.
"We understand that this is a small part of the community," he told Radio 6PR.
"The perpetrators of this attack are not representative of the Australian mainstream community."
Dr Khan said just as the Christian faith preached "turning the other cheek", the Koran said "we will turn an enemy into a friend".
"This is our message of peace and tolerance," he said.
"We will go about business as usual because we understand the aim of these people is to create disharmony and fear. If we bow to that we are supporting their agenda."
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