Florida lawmakers have given final passage to a gun-safety package that raises the legal age for buying rifles and imposes a three-day waiting period on all firearms sales, while also allowing the arming of some public school personnel.

The bill was spurred by the shooting rampage three weeks ago that left 17 students and staff dead at Marjory Stoneman Douglas High School in Parkland and led to an extraordinary lobbying campaign by young survivors of the massacre.

It came on the day a grand jury in Fort Lauderdale formally indicted 19-year-old Nikolas Cruz over the shooting.

Cruz was charged with 17 counts of murder and 17 counts of attempted murder and faces a possible death sentence if convicted.

But the legislation, while containing a number of provisions student activists and their parents had embraced, left out one of their chief demands – a ban on assault-style weapons like the one used in the February 14 massacre.

Supporters have defended the bill saying most school shootings are committed with handguns.

The bill also overcame strenuous objections to provisions permitting school staff to carry guns on the job, a measure critics see as posing a particular risk to minority students who they say as more likely to be shot in the heat of a disciplinary situation or if mistaken as an intruder.

Swift action in the Republican-controlled statehouse, where the National Rifle Association has long held sway, signalled a possible turning point in the national debate between gun control advocates and proponents of firearms rights enshrined in the Second Amendment of the US Constitution.

The measure narrowly cleared the state Senate on Monday and was sent to the desk of Governor Rick Scott, also a Republican, on Wednesday’s 67-50 vote in the Florida House of Representatives.

The bill automatically becomes law within 15 days unless the governor vetoes it.

A spokeswoman for Scott said on Tuesday he had not yet decided whether to support the bill.

Another shooting in Alabama

Two students were shot at a US high school Thursday as the man charged over the Florida school massacre was charged with 17 counts of premeditated murder.

Huffman High School in Birmingham, Alabama was locked down after a shooting incident that left a 17-year-old girl dead and a 17-year-old male student injured.

Birmingham Interim Police Chief Orlando Wilson told a media conference authorities were yet to determine whether the shooting was accidental or if a gun, since recovered by investigators, was intentionally discharged.

“Right now we have a lot of unanswered questions,” Mr Wilson told reporters. “This should not happen in schools.”

He declined to say who fired the gun or to identify what type of firearm it was.

Birmingham Mayor Randall Woodfin said the female student would have turned 18 in roughly 30 days and that she had “aspirations and dreams to be a nurse.”

“We are not just talking about some person, talking about losing a part of our future. Our hearts are heavy. I think it’s really important we find a way to mourn with this family,” Mr Woodfin said at the news conference.

Cruz willing to plead guilty

Back in Florida, the lawyer for the accused Parkland shooter said Cruz is willing to plead guilty if prosecutors take the death penalty off the table, which would mean a life prison sentence.

The Broward County state attorney has not announced a decision on whether he will seek the death penalty.

According observation documents of his time in Broward County jail obtained by CNN, Cruz has been segregated from other inmates due to his high-profile status.

In the report, prison deputies described the inmate as “well-groomed” soft speaking and had a “quiet demeanour.”

Another deputy noted that he “avoids eye contact” and that he “often sits with a blank stare, appears to be in thought”.

It said his speech was slow and “sometimes slurred”.

“Inmate nods his head as a response initially but uses normal speech when prompted,” one deputy said.

The indictment comes as the names of the 17 victims of February’s mass shooting were displayed in a series of digital billboards in New York City’s Times Square.

Today we are proud to have helped, even in a small way, the Alumni of #StonemanDouglasHighSchool show these touching thoughts in #TimesSquare for the world to see. These messages will be playing all day (March 6th). Stay #MSDSTRONG #NeverAgain #BigSignMessage pic.twitter.com/5PtVp27VpF

— BigSignMessage (@BigSignMessage) March 6, 2018

According to local media reports, Big Sign Message donated the billboard memorials for free after being approached by Marjory Stoneman Douglas alumni, who designed the signs.

-with AAP