Can I be fired 3 days after handing in a "temporary full disability note" from my doctor?

On May 17th, 2011 I handed into my employer a note from my doctor placing me on temporary full disability. On May 19th. 2011 I received a work email with the following:

Jeremy
I am assuming at this point that you are able to get to your Hopewell precision emails. I will also mail to you by us mail..
At this time, due to the work load, I can no longer get by without a second person in quality control. We have demands being placed on us by our customers that just can’t wait. Given that your recent medical issue will keep you out of work for an extended time, I will have to move on and find someone else for the position.
We will make your last day of employment, last Friday , May 13th.
I will need your uniforms and your laptop returned.
Sanjita will forward the cobra forms to you. Should you need a letter of recommendation, please feel free to ask.
We wish you well and hope for your speedy recovery.
All the best
Rick


Is this legal?