Noted gun writer, tactics instructor & sworn LE officer Massad Ayoob of NH as a few articles & blog items about this topic.
Ayoob wrote about a sworn LE officer who emptied a pump 12ga at a violent subject less than a car length away and MISSED.
Stats change often. In general I heard US police miss the target with the first fired duty round 75% of the time.
That may seem high but keep in mind that working cops draw firearms 100s of times but rarely if ever fire the sidearms.
Research the recent New York City Empire State Bldg event in 2012. A few bystanders were wounded by the NYPD officers shooting 9x19mm pistols.