(WTVO) — A trail of social media videos by Highland Park shooting suspect alluded to mass shootings and violence.

One of them is a music video featuring a stick figure with an automatic rifle and a figure of someone dying. Authorities said that it is important for people to speak up if they see something disturbing that threatens other people’s safety.

Threats can come in multiple forms, including written posts, videos or pictures. Residents who believe an act of violence is imminent and have a sense of a target, an area or city, should call 911 immediately.

“They should notify local law enforcement and that’s when we get involved and we conduct an investigation,” said Deputy Chief Christopher Covelli of the Lake County Sheriff’s Office. “Law enforcement is going to do everything we can to ensure the community is kept safe, but if we don’t know about it, it’s hard for us to investigate.”