Mass Spectroscopy peak assignments in but-3-en-1-ol i have the mass spectrum for the molecule but-3-en-1-ol. The Mr of this is 72

There are four peaks that are labelled which I have to name the species responsible for forming that peak.

The peaks are:
m/z = 66
m/z = 67
m/z = 71
m/z = 73 - this peak is labelled as (M + H)^+

My answer so far...
The peak at m/z=73 is the but-3-en-1-ol with one added hydrogen, somewhere to the double bond?
For the other peaks am I just removing hydrogens as the mass only decreases by 8 in total so i couldn't remove a carbon or the oxygen.

Does this mean that the peaks are:
m/z=71 is the removal of 1H
m/z=67 is the removal of another 4H (5H in total)
m/z=66 is the removal of another 1H (6H in total)  

is this is correct? Which hydrogens are removed first and what does each species look like for each peak, and are there any charges on the species produced. Also is there a special name for this sort of fragmentation, e.g alpha cleavage?
As you have pointed out, the peak at M = 73 is M+H, protonation is however more likely to occur at the oxygen atom. 



In my opinion, peaks at M = 66 and 67, i.e. with a rather small mass difference to $\mathrm{M^+}$, are negligible.

Common sense and the link in permeakra's comment suggest that the major fragmentation of but-3-en-1-ol occurs along the red dotted line, yielding an allylic and a hydroxymethyl fragment.