St Louis Police Chief Sam Dotson said in a tweet that officers had responded to a call and found an apparently agitated man, armed with a knife who yelled "kill me now" and approached the patrol.
In a tweet from his own account retweeted by his force, Dotson said: "Officers gave suspect verbal commands. Officers feared for their safety and both officers fired their weapons. Suspect is deceased."
Onlookers gathered at the yellow incident tape sealing off the scene of today's shooting outside a convenience store in St Louis, some of them chanting the slogan of the protests: "Hands up, don't shoot."
On August 9, a white officer in Ferguson shot and killed an 18-year-old unarmed black student, triggering more than a week of sometimes violent protests against heavy-handed police tactics.