(Reuters) - A few U.S. states have laws allowing police and family members to obtain orders barring people suspected of being a threat from possessing guns, but Florida does not. Some gun control proponents and legal experts said Wednesday’s school shooting might have been thwarted if it had.

Crosses for the victims of yesterday's shooting at Marjory Stoneman Douglas High School hang on a fence a short distance from the school in Parkland, Florida, U.S., February 15, 2018. REUTERS/Jonathan Drake

Suspected shooter Nikolas Cruz’s history of violence in school and disturbing social media posts would have allowed authorities to prevent him from legally obtaining a firearm in California and Connecticut, which have gun violence restraining order (GVRO) statutes, the experts said.

The killing of 17 students and staff members at Marjory Stoneman Douglas High School in Parkland, Florida, could give new momentum to such laws.

A federal GVRO law was proposed last year, and its supporters in Congress on Thursday urged its passage.

“Americans are grappling today with the fact that multiple warning signs failed to stop a young man from killing 17 students and teachers at a Florida school,” said Representative Don Beyer, a Democrat from Virginia, in a statement.

The National Rifle Association and other groups have opposed such laws as violating gun owners’ due process rights. A judge can issue an initial restraining order and confiscation of firearms without a hearing.

The NRA did not respond to a request for comment on Thursday.

Florida gun rights advocate Jon Gutmacher dismissed the idea that a GVRO law would have stopped the Parkland shooting.

“Intervention, counseling, and meaningful support are our only hope at preventing these things,” he said.

A large number of states have laws allowing gun confiscation in cases involving suspected domestic violence or stalking offenses. GVRO codes allow such an order to be issued when a person more broadly poses a risk to themselves or others.

Connecticut, Indiana and Texas allow law enforcement to seek such an order. California, Washington and Oregon extend the right to family, household members, and domestic partners.

The initial hearing takes place without the subject present, and the subject usually will not learn a restraining order has been issued until police contact them about turning over their guns. A hearing will then follow two or three weeks later, after which the order may be vacated or extended for up to a year.

Former classmates described Cruz, 19, as troubled and “crazy about guns” - talking a lot about firearms and knives.

One of the school’s math teachers told media that Cruz had been banned from returning to campus after he threatened students last year and that administrators sent an email to teachers, warning them about Cruz.

Cruz may have also left warning signs on social media. A person with his name wrote a comment last year under a YouTube video that read “I’m going to be a professional school shooter.”

Cruz also participated in paramilitary training with a white nationalist militia called the Republic of Florida, a leader of the group said on Thursday.

If Cruz had lived in California, for example, a report by a household member or police officer would have been sufficient grounds for preventing Cruz from obtaining his AR-15 assault rifle, said John Donohue, a professor at Stanford Law School.

Cruz’s YouTube comment was reported to the FBI in 2017 but FBI Special Agent in Charge Robert Lasky told reporters on Thursday that investigators were unable to find Cruz based on the comment.

The comment was likely too vague to trigger FBI action even if the agents had been able to locate him, said James Jacobs, a law professor at New York University School of Law.

Two Democratic lawmakers in Florida proposed GVRO bills for that state in October. Hearings have yet to take place, but Patricia Brigham, co-chair of the Florida Coalition to Prevent Gun Violence, said the proposals face long odds in a statehouse controlled by Republicans who tend to toe the NRA line.

Florida Governor Rick Scott’s office did not respond to a call seeking comment.

“Florida should absolutely enact one ASAP,” said Kris Brown, co-president of the Brady Campaign to Prevent Gun Violence, one of the largest gun control groups. “If one had been in place in this case, we do believe it would have had the potential to save lives.”