[C# Skype API] Programm schreibt Nachricht doppelt

using SKYPE4COMLib;
using System;
using System.Windows.Forms;

namespace SkypeBot
{
    public partial class Form1 : Form
    {
        private Skype skype;
        private const string trigger = "#";
        private const string nick = "[BOT] Oneiiros: ";

        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            skype = new Skype();
            //Protocol version
            skype.Attach(8, false);
            skype.MessageStatus +=
                new _ISkypeEvents_MessageStatusEventHandler(skype_MessageStatus);
        }

        private void skype_MessageStatus(ChatMessage msg, TChatMessageStatus status)
        {
            label1.Text = "Got a message"; //nur zu Testzwecken
            //wenn Nachricht mit Trigger startet....
            if (msg.Body.IndexOf(trigger) == 0)
            {
                label2.Text = "Message starts with a trigger"; //nur zu Testzwecken
                //trigger entfernen, command zu lowercase
                string command = msg.Body.Remove(0, 1).ToLower();
                label3.Text = "Command is: " + command; //nur zu Testzwecken
                //schreibe Antwort
                skype.SendMessage(msg.Sender.Handle, nick + ProcessCommand(command));
                label4.Text = "Response sent"; //nur zu Testzwecken
            }
        }
        private string ProcessCommand(string str)
        {
            string result;
            switch (str)
            {
                case "help":
                    result = "---HELP TEXT---";
                    break;
                case "test":
                    result = "It's alive!";
                        break;
                default:
                        result = "Unknown command, #help for help.";
                        break;
            }
            return result;
        }
    }
}