Gas canisters are worldwide used as a measure of dispersing rioting crowds. They are non lethal provided that the rioter do nt remain exposed for too long and doesn't suffer from asma or other respiratory diseases. I bet that also your country's police is equipped with them. And yes, throwing stones is violent.
Two Turkish soldiers, five Kurdish militants killed in attack (Reuters)
from the article: 11 Israeli activists arrested after protest at home of U.S. ambassador