( CNN ) -- A man stabbed four people aboard an Amtrak passenger train from Chicago , including the conductor , authorities said . The train was on its way to Port Huron , Michigan , when Amtrak called 911 on Friday night to report a passenger who appeared agitated , CNN affiliate WBND reported . It stopped in Niles , Michigan , where police responded to the scene , authorities said . By the time they arrived , the man had stabbed several people . The three men and one woman were hospitalized , but their condition was unavailable . One of the men was the conductor , the affiliate reported . The suspect is a 44-year-old from Saginaw , Michigan , according to the affiliate . It 's unclear what his motive was . CNN 's Greg Morrison contributed to this report .
The train was on its way from Chicago . Note : Amtrak called here to report a passenger who appeared agitated . It 's unclear what the cause was .