Mahmoud Dib , 27, had been charged with six firearm offences after a semi-automatic pistol was found in a car connected to him, police said. He was also being investigated in relation to a string of drive-by shootings.Superintendent Angelo Memmolo said tests were under way to determine if the gun had been used in a spate of shootings at houses and cars in Sydney's western suburbs last week. Police said another incident occurred on Monday night, when four shots were fired at a house. No one was injured and there have been no arrests.The shootings are believed to be part of a dispute between the Bandidos and a gang called Notorious. Police said shots were fired into Dib's house on 16 March and they suspect some of the attacks have been reprisals.A standing state commission into organised crime opened a new investigation into biker violence today following the airport brawl.The men the airport shortly after Anthony Zervas, 29, the brother of a well-known Sydney biker, was struck with metal poles. He died in hospital.Biker gangs have existed in Australia since the late 1960s and turf battles have ebbed and flowed. Gang members are often accused of being involved in drugs, although gang leaders deny involvement in organised crime and say they cannot control individual actions.With the exception of a full-blown gun battle in a Sydney car park in 1984 between Bandidos and Comancheros, most violence had been largely out of the public eye.According to Arthur Veno, the author of the 2004 book The Brotherhoods: Inside the Outlaw Motorcycle Clubs, the emergence in the past few years of Notorious has contributed to an escalation of violence and a worrying trend of indifference to the safety of bystanders. Notorious was a shadowy group that modelled itself structurally on a biker gang but was more involved in crime that motorcycles, Veno said.Rudd and the New South Wales premier, Nathan Rees, said tougher laws against gang violence would be considered in the coming months and the federal home affairs minister, Bob Debus, said airport security would be reviewed.