The stories and news reports I heard and read, all reported that the owner went outside to smoke a cig, noticed his garage door ajar, spotted bloody clothing, called 911, and the search led to the discovery of the suspect in the boat.
Some slight variations from numerous threads and reports:
Owner noticed the storage shed door [not garage door] opened and noticed the boat tarp ripped.
Owner also saw blood smears on shed door and/or the boat.
Owner went to check out the tarp rip, lifted the tarp and saw a body (could not tell whether it was alive or dead).
Owner went back into house where he or his wife called 911.