A school shooting in Parkland, Florida earlier this year left 17 people dead.
It was a massacre carried out by a former student known to have a history of behavior issues.
Before that, it was Sandy Hook, where 27 people were killed by a shooter described as uncomfortable socially.
In 1999, violence came to Columbine. It led to 15 deaths by two gunmen, who talked about and wrote about violence.
Together, the three shootings resulted in dozens of deaths and some common links.
"Mental health issues related to this are often a disruptive social environment, whether it be with the family or with friends," Menasha psychologist Frank Cummings said.
Cummings said strained relationships with those family members or friends can become a high risk factor for mental health issues.
"Kids need to know that there's reliability, there's safety, they're cared for, they're loved," Cummings said.
Without that strong social environment, disruptive behaviors can emerge - things like violent actions, threats, or a lack of self control. Cummings said that after seeing those signs stepping in isn't always easy.
"Making sure that 'Johny' gets the help he needs can be a real challenge for some parents because they don't want to admit that their kid has a problem or there's a problem in the home," Cummings said.
Doing something when you see problems like violence or threats can be essential.
"What you do as a parent is you make sure that you have your own support system and you reach out and utilize those resources," Cummings said.
Resources available locally include several behavioral health therapists. Another resource for parents is in the classroom. Officials at the Green Bay Area Public School District say the issue of mental health is a top priority for school safety.
"Number one, absolutely number one," Vicki Bayer said. "We've done a lot of research over the last year exploring what are the patterns in the person that's done the school shootings, often times there are identifiable steps along the way with mental health issues."
School officials said that right now, six schools in the district have a partnership with community providers to bring mental health services into schools. They hope to add the service to more schools. Officials say the district is here to help.
"It's the old see something, say something," Bayer said. "If I'm a parent and I have a concern about my child, I need to reach out. If I don't know where to go, come to your school student services staff - child councilor or your child's school social worker."
Cummings said that the relationship between parent and school official should start right away.
"I think it's crucial to have a proactive relationship the first time they walk in the door, whether they be three or four or five years old," Cummings said.
Cummings also said that some of the early warning signs of mental health issues can be solved with good parenting. He encourages parents to reward kids for positive behaviors but also to correct or discipline what he calls unhelpful or off-task behaviors. He said those consequences should be immediate.