The chief stood with Mayor Sam Adams and answered media questions yesterday during a hastily called press conference as detectives continued to investigate the shootings and prepare them for grand jury review. There were six officer-involved shootings in 2010. Four of those ended with fatalities. There were two officer-involved shootings in the first two days of the new year. It was the most officer-involved shootings in a short period of time — five people in the past 40 days — since 2005, when there were five in a 50-day period. The city auditor will contract with the California-based Office of Independent Review to conduct a review of Portland officer-involved shootings starting in 2004. A separate group of local police and mental health experts are in their ninth month of studying how to eliminate unnecessary Portland police encounters with people suffering from mental illness and have reviewed 40 nonfatal encounters since March 2009.