(Vancouver, WA)  --  A Vancouver, Washington dad is facing charges after allegedly assaulting his 5-month-old son.  Police arrested 36-year-old Aaron Thornewood Tuesday on charges of second-degree domestic violence child assault.  He pleaded not guilty to the charge in court yesterday.  Authorities say his son needed brain surgery to stop the bleeding and to remove a blood clot.  Thornewood says his son received the injury from his two other sons while they were arguing over a toy.