Flowers rest outside of the canceled Astroworld festival at NRG Park in Houston on Saturday. The crowd surge that killed eight people calls to mind other concerts and music festivals that turned deadly in recent decades. Alex Bierens de Haan/Getty Images hide caption
Phoenix police officers stand beside a dump truck blocking a road outside the Phoenix Convention Center on Aug. 22. Protests were held against President Trump as he planned to host a rally inside the convention center. Matt York/AP hide caption
Emergency vehicles navigate the New Year's Eve crowd in Shanghai after a stampede by revelers in the historic riverfront district. At least 35 people were killed. AFP/Getty Images hide caption
Occupy Oakland protesters set trash on fire to make a barricade as police officers form a line to disperse them on Nov. 3., in Oakland, Calif. Kimihiro Hoshino/AFP/Getty Images hide caption