The Guardian has been doing a lot of research on police killing people in the US compared to the rest of the world.
Here's a good summary article:
A few statistics from the article:
Fact: Police in the US have shot and killed more people – in every week this year – than are reportedly shot and killed by German police in an entire year.
Fact: Police in the US fatally shot more people in one month this year than police in Australia officially reported during a span of 19 years.
Fact: Police in Canada average 25 fatal shooting a year. In California, a state just 10% more populous than Canada, police in 2015 have fatally shot nearly three times as many people in just five months.
Fact: Police fired 17 bullets at Antonio Zambrano-Montes, who was “armed” with a rock. That’s nearly three times what police in Finland are reported to have fired during all of 2013.
Fact: In the first 24 days of 2015, police in the US fatally shot more people than police did in England and Wales, combined, over the past 24 years.