When they arrived, they determined the alarm had been triggered by a fire on the top floor of the four-storey structure. A sprinkler head had been activated due to a number of fires that had been intentionally set in one of the suites, said the Chilliwack Fire Department.
A single sprinkler had controlled and extinguished the fires.
Firefighters confirmed the fires were out and shut off the sprinkler system.
Majority of the damage in the unit was related to multiple fires apparently set by the lone tenant, the department said. There was minor water damage to the units below.
Crews from Chilliwack Firehalls 1 and 4 responded to call.
There were no firefighter injuries, and fire officials and RCMP fire investigators are continuing their investigation.