A source of the Salmonella has not yet been identified, however, one major violation was observed - "Investigators found that the restaurant was serving cooked pork prepared at the restaurant owner's home, which is not an approved food safety practice. The restaurant was directed to immediately stop serving pork-based food items and to remove them from their menu."
This practice could be responsible if Salmonella was in the pork or on the packaging. Could be that the smoothies used fresh produce that was not properly washed. If he brought the pork from home, perhaps he bought the strawberries from Uncle Jimmy, who grew them in his garden fertilized with fresh manure.
King County (WA) Public Health Notice
https://kingcounty.gov/depts/health/communicable-diseases/disease-control/outbreak/burien-fresh-smoothies-2018-Aug.aspx
Salmonella outbreak associated with Burien Fresh Smoothies in Burien
King County (WA) Public Health Notice
https://kingcounty.gov/depts/health/communicable-diseases/disease-control/outbreak/burien-fresh-smoothies-2018-Aug.aspx
Salmonella outbreak associated with Burien Fresh Smoothies in Burien