Three days after the unspeakable tragedy in Newtown, Conn., Sen Jeanne Shaheen, the senior senator from the pro-gun state of New Hampshire, proclaimed that the federal government must "get deadly assault weapons off our streets." Oh, boy.

To her credit, Shaheen has not been reflexively anti-gun in the Senate. In 2009 she voted to allow firearms in national parks. And on Monday she indicated that she did not view the problem as entirely gun-related. "We need a comprehensive approach that includes improving access to mental health services, better enforcement of our current laws, and we need to get deadly assault weapons off our streets," she said.

Her first point is an immensely important one. According to a review by the left-wing Mother Jones magazine, 38 of 61 mass-shooting perpetrators in the last three decades had some sort of mental illness. The most horrifying mass shootings in the United States in recent memory - Newtown, Aurora, Tucson, Columbine - all involved shooters with histories of mental problems.

Shaheen has long advocated expanded insurance coverage for mental illness. When she was a state senator she sponsored a bill requiring insurers to cover certain mental health issues, and she signed a law expanding such coverage when she was governor. She brings a lot of experience on this issue that might be useful in the Senate.

However, her statement about assault weapons is concerning. "Asssault weapon" is a term defined many different ways by many different people. If it means "automatic weapon," the federal government bans those made after 1986 already. If it means "semi-automatic" weapon, that would include every firearm that does not require manual cocking or reloading after every shot.

Politicians and anti-gun activists often use vague terms like "assault weapon" to stigmatize broad categories of guns or to hide their own ignorance about firearms. Shaheen needs to clarify what she means by "assault weapons," how she would propose removing them from "our streets," and why she thinks doing so would reduce mass killings.