Mary Ellen-O'Toole believes this shooter didn't just wake up over the weekend and decide to do this. She believes it was well-planned and someone had to have seen a warning sign and spoken up, but didn't.
"Now the warning signs become the responsibility of the people who are close to the shooter. The day, the week, the months before, so that they don't just disregard it as just curious or out of character, but really take the time to notify law enforcement," Ellen-O'Toole said.
You may have noticed firefighters and paramedics rushing into danger wearing tactical gear, including bullet proof vests and helmets.
It is equipment readily available for firefighters in Southeast Wisconsin who can come under fire themselves.
Milwaukee Fire Department has had bulletproof vests and helmets for at least three years. They have not needed to use it yet, and hope it stays that way.
"If were not properly prepared for it, then were doing something wrong," said Deputy Chief Aaron Lipski of the Milwaukee Fire Department.
This tactical gear is one tool of many that first responders are ready to use in an active shooter emergency.
To report any suspicious activity, there is now a hotline state leaders have set up. Click here to find a link.