Most read stories on Columbian.com last week:No. 1) Head-on collision kills driver in HockinsonA woman died and another was seriously injured Saturday morning when their vehicles collided head-on on Northeast 182nd Avenue near 139th Street in Hockinson, according to the Clark County Sheriff’s Office.No. 2) Husband who killed Vancouver native attacked in prison The order barked from speakers in the prison yard: “Stop fighting.” But two inmates kept attacking a third, Brian C. Cole, who had arrived the day before at Snake River Correctional Institution. Cole, 38, was doubled up on the sidewalk, taking kicks to his head and stomach.No. 3) Child sex trafficking on rise in Clark County Over the past three years, police in Clark County have seen child sex trafficking emerge as one of the major crimes to watch. It’s no longer just a Portland problem. Fueled by online ads, johns and girls will routinely travel between Vancouver and Portland for “dates,” making the crime a regional issue.No. 4) Violations found in death of Clark County deputy’s sonA Clark County sheriff’s deputy violated policies on firearms storage, off-duty conduct, ethics, competency and employee responsibilities in connection with the 2010 shooting death of his 3-year-old son, according to an internal affairs investigation.No. 5) I-5 south ramp to Fourth Plain reopens after rollover accident The southbound ramp from Interstate 5 to East Fourth Plain Boulevard was temporarily closed Monday afternoon because of a crash involving a 2004 Chevrolet Impala.