Water cannons and tear gas are often used in conjunction with other crowd control methods, such as batons and shields. They can be especially effective at dispersing large crowds or crowds that are resisting arrest.
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There have been numerous reports of water cannons and tear gas being used excessively or in a discriminatory manner. For example, in 2014, police in Ferguson, Missouri used tear gas and rubber bullets to disperse peaceful protesters following the death of Michael Brown. In 2019, police in Hong Kong used water cannons and tear gas to disperse pro-democracy protests.