Police found the 49-year-old man shot to death in his Scopus, Mo., residence late Friday night.
They were responding to a frantic 911 call from Strong's girlfriend, who said she heard Strong yelling at someone to get out of his house, and then heard a gunshot.
Police have spent the past three days following leads and gathering evidence.
"We've pretty much been going around the clock," said chief deputy Leo McElrath of the Bollinger County Sheriff's Department.
The Major Case Squad spent Monday compiling financial records, wills and other documents in the hope of finding why someone might have killed Strong.
"We're searching for anything that could lead to any kind of a motive," said McElrath.
Authorities ruled the cause of death as a single gunshot wound to the head.
After the autopsy, they discerned the killer had shot Strong with a high caliber revolver, McElrath said.
A foot search of the house and surrounding property by police yielded no new evidence.
Strong's family declined to comment at this time.
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