mongoid update all documents with conditions

I have a model

class Employee
  include Mongoid::Document
  field :first_name
  field :last_name
  field :address1
  field :address2
  field :salary
end

Now I need to update all Employee's salary to 10000 whose address1 is "Calgary"

Now I tried this query

Employee.update_all "salary = 10000", "address1 = 'Calgary'"

But this query gave me error as:

NoMethodError: undefined method `update_all' for Employee:Class

Thanks