Several schools went into lockdown before more than a dozen Armed Offenders Squad officers stormed the Breens Rd property just before 4pm.
A man and a woman were ordered to get on the floor.
Police searched the house but it doesn't appear that the alleged gunman was found.
The couple were spoken to by police.
A father of a Breens Intermediate School pupil found himself caught up in the raid.
He'd been texted at 3.05pm that the school was in lockdown.
Waiting outside the gates, he saw police. They told him they were looking for an armed man.
He drove back down the road to get out of their way.
But soon more than a dozen black-clad armed officers lined up outside a Breens Rd flat near Lochmore St.
He asked them if he needed to move but they suggested he stay put with the windows up.
"They had a ramming thing and a few went into the neighbour's garden and surrounded the place," he said.
It's the second time his daughter's school has been locked down in recent months - with the same happening after the March 15 mosque shootings.
"She'll be panicking," he said.
A black Suzuki Swift with a badly damaged right rear wheel was parked just down from the raided flat.
Children of Isleworth Primary have now been allowed home.
