Madison Police Chief Shon Barnes said investigators were working with the Bureau of Alcohol, Tobacco, Firearms and Explosives to determine the origin of the weapon allegedly used by 15-year-old Natalie Rupnow on Monday.

According to authorities, Rupnow opened fire with a handgun at the school, killing two people and wounding six more before killing herself.

The police chief added that he believes children should not have access to guns.

“I don’t believe 15-year-olds should have access to weapons that they can take to school and potentially hurt someone. We really need to do a better job, not only in our communities, but in our country, of making sure that our young people don’t have access to guns and firearms, and certainly making sure that we’re looking after the mental health of our children.” , he told CNN.

“We have asked our partners at the ATF to expedite what we call an ATF traceability form to determine the origin of this weapon, who purchased it and how it got from a manufacturer to the hands of a 15-year-old girl.” said Barnes. “These are questions that will take some time to answer.”

Barnes said a media briefing will be held at 12 p.m. CT (1 p.m. ET) to provide further updates on the investigation.