Four cops from Uppsala, Sweden, were on a New York City subway headed for a Broadway show when they heard a subway conductor over the intercom ask if there were any police officers aboard. Going over to investigate, the four cops found a homeless man assaulting another homeless man who was offering no resistance. The four broke up the fight, with two holding the attacker until police arrived and the other two tending the victim. The incident was caught on video:
Pretty standard stuff, except that we know it could've turned out differently. De-escalation is far from a universal tactic taught to American police, although a number of departments began training it after Ferguson became a national news story. The failure to de-escalate increases the likelihood of deadly force being used, and is rooted in the failure to differentiate between the ability of the police officer, technically a trained professional, to act toward de-escalating the situation and the ability of the suspect, often someone in a poor state of mind, to do the same. That failure leads to situations like this.