UPDATE | The assault charge against Joseph Kau were stayed by Justice Cathy Mocha on Sept. 16, 2019.

Toronto police have charged Joseph Kau, 46, with one count of assault after a confrontation with a TTC driver on the 511 Exhibition bus on Sept. 3.

The Toronto man previously told CBC Toronto that he was punched in the head by the driver, leaving him with a blood clot in his head.

But police say security footage implicates Kau as the instigator.

"It was determined, through reviewing the video, that Mr. Kau was the aggressor and that's why he was charged," Const. Craig Brister said.

Toronto police say any discipline as far as the driver is concerned will be left to the TTC.

The transit agency says the matter is still under review and any disciplinary action taken would be a personnel matter.

The TTC previously told CBC Toronto any action taken by the driver was retaliation after the rider had spat on him.

"The operator responded, got up, defended himself. And it's about time that people realized that we're not pin cushions, we're trying to do our jobs," said Kevin Morton, the secretary-treasurer for the Amalgamated Transit Union Local 113, adding that the driver was suspended with pay.

CBC Toronto could not independently confirm that Kau suffered a blood clot, but medical records show he went to hospital Sunday night and was then called back for a CT scan Tuesday.

The Toronto man is scheduled to appear in court on October 10.