Close a recently opened process C #

I need to perform the execution of a process for a certain time, for which I start a process, and using a Timer after 10 minutes, I kill it using Kill() , I do it in the following way:

using System.Diagnostics;
using System.Threading;
public class Manager{
    private Process Proceso;

    public Manager(){        
        //Inicio el proceso EdmServer
        Proceso = Process.Start(@"C:\Program Files\SOLIDWORKS PDM\EdmServer.exe");
        //StopProcess se ejecuta tras 10 minutos.
        Timer t = new Timer(StopProcess, null, 600000 , 0);
    }

    private void StopProcess(object o)
    {
        try
        {             
            Proceso.Kill();
        }    
        catch(Exception ex)
        {
            ex.CreateLog();
        }
        finally
        { 
            Environment.Exit(0);
        }
    }
}

The code works as I hope, the issue is that by raising the time I intend to keep the process open, increasing the wait of Timer , when closing the process, the following exception is generated:

  

The request can not be processed because the process has finished.

The issue is, that goes through the finally , the execution finishes, but the process that I intend to close is still open.

Why is the exception thrown if the process did NOT end?