This is becoming a weekly event.  One person with an AR15 semi automatic weapon with a few 30 round clips can wipe out a group of police officers.  The .223 round travels at over 3,000 ft per second at the muzzle.  It is not a good gun for big game hunting because the bullet is too light but it is perfect for killing humans.  As a gun owner and a pro second amendment supporter, I have to concede:  The semi automatic assault rifles and the 30 round clips have got to go.  We are left with little choice.  Background checks do not work!  I think a federal buy back program might work after the assault rifles are made illegal.