“When our children and our grandchildren are at school, we must have faith that they are safe,” Boxer said in a statement after introducing her bill. “This legislation will help state and local officials protect our children by utilizing all of the law enforcement tools at our disposal.”

S. 3692 would allow the federal government to reimburse governors who use National Guard troops to keep schools safe. She said her bill was based on a National Guard program that allowed governors to use the National Guard to assist with law enforcement efforts related to drug crimes.

In Connecticut, the gunman, 20-year-old Adam Lanza, used a high-powered rifle and had an arsenal of hundreds of rounds of especially deadly ammunition, according to reports. He killed himself about 10 minutes after starting the attack.

The Associated Press reported that Lanza is believed to have used a Bushmaster AR-15 rifle, a civilian version of the military's M-16. Some AR-15s were outlawed as part of the 1994 assault weapons ban. But that law expired in 2004, and Congress did not renew it after heavy pressure from gun-rights lobbyists.

Democrats have called for reinstating the assault weapons ban, in addition to other gun-control measures, when Congress begins legislative work next year.