or better still -
take 1 sledge hammer.
swing towards wall
follow through into walk
clean up the mess - as house falls down around you
Edited for truth
Not a good idea to knock solid walls down in houses. They usually are structural, Pin, prop,
add lintel, cut THEN swing the oversized hammers
As to brackets a small steel angles should do it 1" or 1.5" - visit a local metal frabracators
or chainlink fence maker and ask for some off cuts.
But saying that what you've drawn about should work fine if complete length
(stagger fixing along timber) If it weights more that 30kgs add a second fixing bracket.
this small piece (only 250mm long) and its 3 fixings can hold my weight!
I'm no couch potato but i weight a whole lot more that a pc
Also my pc is wall mounted and only held by four 4" screews and is solid as a rock.If the
fixing are arranged in a large square or triangle you can hold significantly more weight
that arrange in a single line (EdGey was spot on with 'twice if not more' with two lines)
as these fixing paturn massively reduces shear loading on any one screw.
Your bigest element of weight will be the wooden front, so keep it as thin as possable - have
you thought about cutting down a door blank into a square?
That way you have only one unfinished edge to repair (and can hide it as the top edge if not
perfect) Just an idea as they come in various widths, some are hollow core, and can be
flush faced or molded (if thats your thing)
Might be worth you reading my build log - might save you making some of the mistakes I did.
Really think about the sequence in which you build - might save you a good few hours