Create a 24 bit bitmap file with a black background using Graphicsmagick

Question

gm convert -size 800x480 xc:black -pointsize 120pt -fill white -gravity center -font Arial -draw "text 0,0 'Harry'" -type TrueColor -depth 24 BMP3:output3.bmp

This code will create a bitmap file output3.bmp. However it is an 8 bit file not 24 bit. I am able to create the file in Windows paint. When I create it in paint this is what I get.

Image: 24Bit.bmp
  Format: BMP (Microsoft Windows bitmap image)
  Geometry: 800x480
  Class: DirectClass
  Type: bilevel
  Depth: 1 bits-per-pixel component
  Channel Depths:
    Gray:     1 bits
  Channel Statistics:
    Gray:
      Minimum:                     0.00 (0.0000)
      Maximum:                     0.00 (0.0000)
      Mean:                        0.00 (0.0000)
      Standard Deviation:          0.00 (0.0000)
  Filesize: 1.1Mi
  Interlace: No
  Orientation: Unknown
  Background Color: white
  Border Color: #DFDFDF
  Matte Color: #BDBDBD
  Page geometry: 800x480+0+0
  Compose: Over
  Dispose: Undefined
  Iterations: 0
  Compression: Undefined
  Signature: 89b0739176878b3715148cddb439c7a44cce2af130ee745527e854c73d471ec3
  Tainted: False

How can I get this type in Garphicsmagick?