A home raided by heavily armed police officers as part the investigation into the death of police accountant Curtis Cheng was targeted several months ago in a firearms search.

The dual-level home on Lockwood Street, Merrylands, was surrounded by tactical police about 6am on Wednesday before two men were searched, handcuffed and led away.

Talal Alameddine, 22, and Rafat Alameddine, 24, are being questioned by detectives at a Sydney police station.

The arrests come as police investigate where the gun that Farhad Jabar, 15, used to kill Mr Cheng came from.

Police sources say they believe the gun was acquired from a Middle Eastern crime gang and was given to Jabar.

Rafat was detained as a result of an outstanding warrant for identity fraud and other fraud matters.

Fairfax Media understands the Alameddine household was targeted in a firearms raids in February after police received a tip-off about potentially dangerous disruptions to court hearings at a Sydney court complex.

A resident who lives across the road from the Alameddines confirmed police had raided the property in February.

"This is not the first time it has happened," he said.

"It happened [in February] over something to do with a court case in the city."

On that occasion, police were searching for "prohibited firearms" and also searched another property. No one was charged with any offence.

The night before, it is understood detectives from the State Crime Command received a tip-off that the Downing Centre Court, which was hearing a court case involving two men with lengthy criminal histories, could be disrupted, including a possible shooting.

Fairfax Media understands police were left with no choice but to then throw immense police resources at the court complex to prevent any disturbance.

Police are still searching the Merrylands home, with forensics arriving a short time ago and officers searching through three cars.

Residents say police arrived outside the home just before 6am on Wednesday and used a megaphone to call the occupants outside.

"They said, 'Residents of number ... come out, your house is surrounded, you will not be harmed,' " one resident said.

The man said three boys came out of the house one by one and were searched before being led down the street by police.

One of the women who walked out of the house clashed with reporters on the street, grabbing a journalist's microphone and pushing a camera away.