I strongly disagree. Sure, you can use tear gas to kill, just as you can use water to kill. And guess what, dispersing a crowd with a fire hose is equally indiscriminate as to whom you hit (and god forbid you hit a baby with it). But to call it a terror weapon and invoking war crimes is a ridiculous hyperbole.
The atrocity is what you do with it, not what it you use.
Yes, they are. I've been saying that. Gangs are states for people the de jure state cannot or will not cater to. The mafia started as local enforcement during a period of state failure in Italy, yakuza started as a sort of trade guild for gamblers and peddlers, etc. Which is why I've been saying that if we had a functioning state that could actually provide basic human rights and services to its entire population, most of the violence we think we need an unaccountable paramilitary for would go away.
This includes serial killers, because serial killers are an artificial category created by the FBI and maintained by a media industry that makes money talking about them. There is no mysterious chunk of the population born without souls.
Serial killers are no more an artificial category because it was invented by the FBI than other word because it was invented by someone. Not all people in the world are lovely fluffy bunnies that just need love. They are however just individuals, hated even by other criminals so are of little relevance except as a sign of wider societal corruption.
Gangs are what states exist to prevent from happening. Perhaps gangs in some cases turned into states, but this is rare because gangs are noncompetitive with states; pretty much always an existing state eradicates the gang long before it can evolve into a state. Gangs are uncompetative because they are based upon antisocial behavior and so destroy the society they rule over, causing it to become too weak to support the gangs ability to mantain control of it's territory. States by contrast are based upon prosocial behavior, causing them to become too powerful for gangs to prevail against in most cases.
The problem is that states become a victim of their own success. Once people are all lovely and safe, people start to resent being governed at all and seek to throw everything into chaos, either because they have better State in mind or they are Anarchists that believe all their prosperity and security is not owed to any State at all. In reality they achieve the exact opposite of their aims, rule by a criminal gang; which is what defunding/abolish the police department will get you Americans if you continue with this foolishness.
Ironically here in Britain our own shrink-the-state austerity party defended the police forces which quite predictable consequences (crime, especially violent crime went up).