Late last month, the Fond du Lac Police Department got a tip that a 15-year-old had threatened to carry out a mass shooting. Lieutenant Nick Hahn says investigators took this threat seriously."On this situation our detectives go t the tip, started looking into it right away," Hahn said. "And they realized that the threat assessment was going up as they as they looked more at the facts."Hahn says the tip originated from someone outside the United States.WATCH JACK PORTER'S FULL BROADCAST STORY HERE: Fond du Lac police investigate alleged mass shooting threat by 15 year oldBecause of those international ties, he says around six or seven agencies, including the FBI and ATF, were involved in the investigation.The day after the tip, they executed a search warrant at the teen's home and seized multiple firearms, a computer and a cellphone.Experts say it's important for parents or friends to watch out for warning signs regarding a child's mental health.Dr. Matthew Doll, a clinical psychologist at SSM Health, says having that conversation is the first step."Are you doing okay? Is there something going on that we can talk about. And then really create a safe space. it's always about relationships," Doll said.While Doll stated every instance is different and unique, people should always approach these conversations in an understanding, supportive and observant way."We also want to keep an eye on some warning signs," Doll said. "When kids become preoccupied and have a particular focus. where they seem to be angry or change in functioning."Police have not indicated where the teen in this case planned to carry out those threats.Hahn says the investigation is still ongoing and the public will receive more information as it becomes available.No charges have been filed against the 15-year-old, as of the time this article was published. ...read more read less