Footage from the scene showed the two men laying on the floor covered in blood surrounded by paramedics.
"On our arrival we found two male patients … with multiple gunshot wounds to multiple regions of their bodies," NSW Ambulance inspector Kevin McSweeney said.
"They were both found to be in extremely critical condition. At the scene we stabilised the patients as best we could.
"When we arrived on scene both patients had suffered significant blood loss and one of them had gone into traumatic cardiac arrest.
"Paramedics did everything they could but despite best efforts, he died at the scene.
"The second patient had been hit with up to 10 bullets and incredibly, was still conscious and breathing when we transported him to hospital.
"This was an horrific and confronting scene that unfolded in front of several witnesses, it is very fortunate no other members of the public were injured."
Two burnt out Audi Q7 cars, believed to be linked to the shooting, were found in Berala and Greenacre not long after.
The shooting comes a week after The Daily Telegraph reported that a bounty had been placed on Tarek's head.
A bikie source told the newspaper he had been warned by those close to him to play it safe.
"They warned him the other week, 'Stop going to the gym, change your routine', but he didn't listen. They are fuming," they said.
Police and paramedics at the scene where Comanchero bikie Tarek Zahed and brother Omar were shot in Auburn. Photo / Supplied
Tarek, the sergeant at arms of the Comanchero in Australia, had reportedly been tipped to become the next national president.
According to The Daily Telegraph, the decision by the bikie gang to team up with the Alameddine clan to dominate Sydney's drug market earned them many new enemies.
The Almeddine clan has been involved in a brutal war with the Hamzy organised crime network that has resulted in 11 suspected killings, police believe.
NSW Police has established Strike Force Leary to investigate the shooting, with the Homicide Squad to be assisted by officers from the Criminal Groups and Raptor Squads, as well as Auburn Police Area Command and South West Metropolitan Region.
Police Commissioner Karen Webb and Police Minister Paul Toole will hold a press conference in Parramatta at 12.30pm (Australia time) to announce additional measures to combat the ongoing gang warfare.
"An immediate operational response is underway, which includes intelligence-based targeting of known members and associates of involved criminal networks," NSW Police said in a statement.
Bullet holes can be seen in the glass doors. Photo / Supplied
Commissioner Webb told 2GB's Ben Fordham on Wednesday morning an additional 30 officers would be added to Strike Force Raptor in the wake of the shooting.
"Enough is enough," she said.
"The community in southwest Sydney, western Sydney and Sydney in general have had enough. We're just going to keep tackling this."
Commissioner Webb confirmed police had attempted to warn Tarek.
"In this organised crime world, information does come to police and we try and pass it on and let people know," she said.
"I understand Tarek had been overseas and he'd come back and was living in Victoria. He'd come back to Sydney. Some of these people think they're invincible, I think, larger than life. What else can you do when you try and warn them but they just live their lives like they're larger than life. But life of crime's not worth it, Ben."
Commissioner Webb said it was too early to say whether Tarek's shooting was revenge for underworld figure Mahmoud 'Brownie' Ahmad, who was gunned down in Greenacre less than a fortnight ago after also being warned of a multimillion-dollar bounty on his head.
"Well we can't rule it out, but some of these people are in conflict with a number of other groups so it's hard to pinpoint whether it's actual direct retaliation or not, but certainly a line of inquiry for us," she said.
NSW Labor police spokesman Walt Secord said he was worried about a member of the public being hurt in gangland shootings.
"Crime gangs are carrying out attacks with impunity and with no regard for the safety of others," he said in a statement.
"Frankly, I'm less concerned about feuding gangsters killing each other and far more concerned about innocent bystanders getting killed in the crossfire.
"The community has been patient. The wave of shootings has gone on too long. This is about community safety."
Late last month, Tarek was charged with allegedly contravening a serious crime prevention order, after failing to notify police that he was moving residence while visiting NSW.
He was one of two senior bikies set to face court after police launched a crackdown on organised criminal networks following Ahmad's shooting in Greenacre.
Tarek was due to appear at the Downing Centre Local Court on June 22.
Police Minister Paul Toole said after the raids that Ahmad's death strengthened authorities' resolve to arrest and charge people.
"The message is simple - if you're even remotely associated with organised crime, police are watching, they have leads, and they will act," Toole said.
