Media playback is unsupported on your device Media caption Seven things the NRA blames after Florida

The head of the most powerful gun lobby in the US has accused Democrats and media of "exploiting" a Florida school shooting that left 17 people dead.

Wayne LaPierre said "opportunists" were using the 14 February tragedy to expand gun control and abolish US gun rights.

Mr LaPierre's comments came during the Conservative Political Action Conference (CPAC) in Washington.

Meanwhile, US President Donald Trump suggested teachers could receive bonuses for carrying guns.

"As usual, the opportunists waited not one second to exploit tragedy for political gain," said Mr LaPierre, who is head of the National Rifle Association (NRA).

"They hate the NRA. They hate the second amendment. They hate individual freedom," he said, referring to the second amendment in the US constitution, which governs the "right to keep and bear arms".

Separately, it has emerged that an armed guard who was at the school during the shooting stood outside the building where the attack was taking place and did not go in to confront the gunman.

Scot Peterson, the school resource officer, has now resigned after being suspended, Broward County Sheriff Scott Israel said.

"I am devastated. Sick to my stomach. He never went in," Sheriff Israel said. He was quoted by the Miami Herald.

Media playback is unsupported on your device Media caption Florida shooting: Why the NRA wields so much power

Mr LaPierre's comments were the gun lobby's first more than a week after the massacre at Marjory Stoneman Douglas High School in Parkland, Florida.

Mr LaPierre lambasted the FBI for failing to follow up on a tip about the former student suspected of carrying out the attack.

He also criticised America's "European-style socialists" for urging gun control.

"They don't care if their laws work or not," said Mr LaPierre. "They just want to get more laws to get more control over people. But the NRA, the NRA does care."

Survivors of last week's deadly shooting have called for stricter gun laws, prompting the nationwide activist movement #NeverAgain.

Mr LaPierre accused Democrats of trying to smear the NRA.

Mr LaPierre reiterated the NRA's backing for the proposal of arming teachers.

He said the NRA would help any US school with their safety and security, free of charge.

Media playback is unsupported on your device Media caption Teacher at Florida school where 17 people died says arming some teachers would be wrong

"Evil walks among us and God help us if we don't harden our schools and protect our kids," he said.

But Randi Weingarten, president of the 1.7 million-member American Federation of Teachers union, disagreed.

"Anyone who wants guns in schools has no understanding of what goes on inside them - or worse, doesn't care," she said.

What did Trump say?

The US president has stepped up his calls for teachers to be armed, a day after he floated the proposal at a White House event to hear from survivors of the Florida school shooting.

Discussing school safety with state and local officials on Thursday, he said: "Shooters won't walk into a school if 20% of people have guns."

Mr Trump added: "What I'd recommend doing is the people that do carry, we give them a bonus. We give them a little bit of a bonus."

The president also said he supports raising the age at which a person can buy a gun from 18 to 21, insisting the NRA would back such a proposal.

"I don't think I'll be going up against them," Mr Trump said of the gun lobby. "They're good people."

Mr Trump also took to Twitter to push for national background checks for the mentally ill, a policy which the NRA chief later echoed at the conference.

"Anyone adjudicated as mentally incompetent or dangerous to society should be prevented from getting a gun," said Mr Trump.

Media playback is unsupported on your device Media caption Victim's father tells Trump of rage

Reshaping the new gun debate

Analysis by Anthony Zurcher, BBC News, Washington

On the first day of CPAC, the NRA had an uninterrupted hour to offer its response to Parkland - and respond it did. In a one-two punch, Dana Loesch and Wayne LaPierre launched a blistering attack against the mainstream media, the FBI and pro-gun-control Democratic politicians.

The media "love mass shootings" because of the ratings, Ms Loesch said. The FBI rank-and-file should rise up against a "corrupt" senior staff that has failed to stop mass shooters, Mr LaPierre railed. Democrats, he said, "hate individual freedom".

Media playback is unsupported on your device Media caption What's Donald Trump said about guns and gun control?

The rhetoric may be an effort to reshape a firearm debate that, over the past week, has shifted towards calls for bans on so-called assault weapons and the emergence of students seeking action on gun control.

The NRA would prefer this to be a conversation about media bias, "European socialist" Democrats and an FBI that has lately become a conservative bogeyman.

When it comes to policy proposals, turning schools into "hard targets" with armed teachers and airtight security is the preferred option.

The NRA has a vast political war chest and a president who views it as a loyal ally. It has been down this road before - after Columbine, Newtown and other school shootings. The NRA's work is just beginning.