A Canadian man killed by police on Wednesday had indicated he planned to carry out an imminent rush-hour attack on a major Canadian city.

The man drew the attention of U.S. authorities who tipped off Canadian police, intelligence sources said.

The man was killed on Wednesday during a police raid in a small Ontario town, the Royal Canadian Mounted Police (RCMP) said, but did not give further details.

According to Reuters, intelligence sources identified the dead man as Aaron Driver, who was arrested last year for openly supporting ISIS on social media.

Driver had been placed under a court order earlier this year restricting his movements.

The U.S. Federal Bureau of Investigations alerted Canadian authorities early on Wednesday that an individual was engaged in potential terrorism-related activities, the sources told Reuters. The sources declined to be identified as they did not have permission to speak to media.

One source said the FBI did not know the identity of the man and sent a wide notice across Canada about the potential threat. A second source said the Canadians then realized it was Driver and deployed to the home in Strathroy, Ontario where he had been living.

“We can confirm a police operation took place in Strathroy yesterday, where a suspect was fatally shot by our officers,” RCMP spokeswoman Annie Delisle said in an email.

“The RCMP and our partners have been working overnight at securing the scene and to gather the evidence to advance/further the investigation.” Strathroy is about 225 km (140 miles) southwest of Toronto.

There were no details yet of what kind of attack Driver, who also used the alias Harun Abdurahman, had allegedly been planning.

Public transit operators in Toronto, Canada’s largest city, were warned by police of potential security threats hours before officers killed Driver, they said on Thursday.

The Toronto Transit Commission (TTC), which serves the city, and the regional operator GO Transit confirmed they were contacted by police early on Wednesday

TTC spokesman Brad Ross said there was no specific threat made and there was nothing to indicate the transport agency was a target. The TTC sent out a “vigilance notice” to all of its employees, Ross said.

GO Transit spokeswoman Alex Burke referred further questions on the matter to the RCMP.

Driver had not been charged with a crime. But in February he was placed on a peace bond, a court order that restricted his movements, required that he stay away from social media and computers and not have contact with ISIS or similar groups.