The father of a Virginia journalist killed in an on-air shooting said on Thursday he would become a crusader for gun control, but analysts said there was little likelihood of legislation on the federal level any time soon, despite changes in some states.

Two journalists, reporter Alison Parker and cameraman Adam Ward of Roanoke CBS affiliate WDBJ7, were shot during a live interview on Wednesday by a disgruntled former station employee who later killed himself. The woman who was being interviewed was wounded and hospitalised.

Parker's father, Andy Parker, urged state and federal lawmakers to take action on gun control, especially to keep firearms out of the hands of people who were mentally unstable.

"I'm not going to rest until I see something happen. We've got to have our legislators and congressmen step up to the plate and stop being cowards about this," Parker told CNN, describing himself as a supporter of the constitutional right to keep and bear arms.

He said the National Rifle Association, the powerful US gun lobby, would probably contend that his daughter and Ward would have been safe if they themselves had been armed.

"It wouldn't have made any difference," Parker said. "How many Alisons is this going to happen to before we stop it?"

The United States had about 34,000 firearms deaths in 2013, with almost two-thirds of them suicides, according to the Centers for Disease Control and Prevention.

Sarah Trumble, a senior policy counsel for the Third Way, a Washington think tank, said prospects for gun control had little chance in the Republican-controlled Congress, despite intense media focus on the Virginia killings.

"There's no playbook for what to do here," she said, but added that changes were more likely in states than at a federal level. "The states are really where the action is."

The last time there was a push at the federal level for tighter gun control was following the massacre of 26 people, mostly children, at the Sandy Hook elementary school in Newtown, Connecticut, in December 2012.

President Barack Obama supported legislation that would have extended background checks for gun buyers and banned rapid-firing assault weapons. But despite national revulsion over the Newtown killings it was rejected in April 2013 by the US Senate, including by some lawmakers in Obama's Democratic Party.

After Wednesday's shooting, Obama reiterated his frustration over the issue of gun violence, saying the United States needs to do "a better job of making sure that people who have problems, people who shouldn't have guns, don't have them".

Measures go ahead

Although the issue is stalled at a national level, gun control measures have gone ahead in the last two years in several US states, with 18 now requiring background checks for the sale of handguns, said Colin Goddard, senior policy adviser for Everytown, a gun control advocacy group backed by former New York Mayor Michael Bloomberg.

Among other gains for advocates of gun control are a 2014 referendum in Washington state for background checks on gun sales in which backers of the initiative outspent the NRA. Oregon's governor in May signed legislation for background checks on almost all buyers.

Nevada voters will go to the polls in a similar referendum next year.

In Maine, Goddard said Everytown had started a campaign to get a background checks question on the ballot. But gun rights advocates notched a victory in the state last month when it became the fifth to allow gun owners to carry concealed weapons without a permit.

In Virginia, where the NRA is headquartered, Democratic Governor Terry McAuliffe called for gun controls after Wednesday's shooting.

But gun control legislation is unlikely to pass the Republican-dominated legislature, said Stephen Farnsworth, a pollster at the University of Mary Washington in Fredericksburg, Virginia.

"It's a very gun-friendly legislature and the shootings this week will do little to change that," Farnsworth said. He added that polls have shown more support for gun control among state residents than among politicians.

Wednesday's shootings were particularly shocking because they happened on air, and because of social media posts about the attack by Vester Flanagan, 41, the man police said carried out the shooting.

His posts illustrated a trend of people wanting to commit murders and post images of the killings online to gain notoriety, Parker's boyfriend, Chris Hurst, told NBC.