(La Crosse, WI)  --  Just across Minnesota's southeastern border, police in La Crosse, Wisconsin say they are making progress in the investigation after a father and son were found shot to death at their photography business.  Authorities say Saturday's killings appear to be an isolated incident directed at May's Photo.  But Police Captain Robert Lawrence says business owners, especially in downtown La Crosse, are alarmed and they're trying to have more of a police presence in that area.  Police are still taking tips from those who have information about the murders of 56-year-old Paul Petras and his 19-year-old son A-J.  There's a memorial service Friday morning in La Crosse.