C# pictureBox shows weird sign trying to show video stream on it

public partial class Form1 : Form {

    FilterInfoCollection videoSources;
    VideoCaptureDevice videoStream;

    public Form1(){
        InitializeComponent();
    }

    private void startStream_Click(object sender, EventArgs e){
        videoStream.SignalToStop();
    }

    private void Form1_Load(object sender, EventArgs e){
        videoSources = new FilterInfoCollection(FilterCategory.VideoInputDevice);
        videoStream = new VideoCaptureDevice(videoSources[0].MonikerString);
        videoStream.NewFrame += new NewFrameEventHandler(videoStream_NewFrame);
        videoStream.Start();
    }

    void videoStream_NewFrame(object sender, NewFrameEventArgs eventArgs){
        Bitmap newFrame = eventArgs.Frame;
        pictureBox1.Image = newFrame;
    }


}