Media playback is unsupported on your device Media caption Andy Parker: ''Mr President, you need to do this, you need to tackle this''

The father of Alison Parker, one of two journalists killed live on air, has appealed to US President Barack Obama to push through tougher gun laws.

"You need to do this... I will help you do this and the press is with you on this because they just lost one of their own," Andy Parker told the BBC.

Staff at WDBJ TV in Virginia have been mourning the loss of his daughter, a reporter, and cameraman Adam Ward.

They were shot dead live on air by a disgruntled ex-colleague on Wednesday.

The attack has reignited the debate about gun control laws in the US.

Image caption Mr Parker, who lost his daughter Alison (pictured), said the US media would support President Obama

Mr Parker acknowledged it would be an uphill battle to change the law, but said the president could take on the challenge as he had with other issues including healthcare reform.

"Mr President, you need to do this. Please do it. Please do it for us and for other people so they're not going to lose their Alisons and their Adams," he said in an emotional message.

President Obama supported legislation to extend background checks for gun buyers and a ban on rapid-firing assault weapons after 26 people were killed at a school in Newtown, Connecticut, but it was rejected in 2013.

Last month, he told the BBC the failure to pass "common-sense gun safety laws" was the greatest frustration of his presidency.

On Wednesday, he said the US needed to do "a better job of making sure that people who have problems, people who shouldn't have guns, don't have them."

Presidential hopeful Hillary Clinton said she would "take on" the issue of gun violence, while admitting it was "a very political, difficult issue in America".

She said: "I want to reiterate how important it is we not let yet another terrible incidence go by without trying to do something more to prevent this incredible killing that is stalking our country."

Republican presidential hopefuls Jim Gilmore and Ben Carson have warned against any rush to introduce tougher gun controls.

Although the issue has stalled nationally, gun control measures have gone ahead in the last two years in several states.

'We will heal'

WDBJ Roanoke news director Kelly Zuber said in a news conference on Thursday that none of her news teams had been doing live shots for the last two days "out of an abundance of caution".

She said the gunman, Vester Flanagan, may have discovered the location of the news crew after watching them in an earlier TV appearance at Bridgewater Plaza in Moneta on Wednesday, and had enough time to drive to the area before their second live appearance.

The station's general manager, Jeff Marks, also said Flanagan had vowed to make "a stink" soon after he was fired from the station two years ago.

Media playback is unsupported on your device Media caption In an emotional broadcast, members of the WDBJ7 team held hands and wiped away tears

Earlier on Thursday, the station held a minute's silence on air in memory of the two slain journalists. "We will, over time, heal from this," WDBJ7 anchor Kim McBroom told viewers, holding hands with two colleagues.

Bunches of flowers and black ribbons have been placed outside the channel's headquarters in Roanoke.

Flanagan, who posted online a video he had filmed of the attack, died from a self-inflicted gunshot wound later on Wednesday.

Memos from the station reveal Flanagan, who used the on-air name of Bryce Williams, had been ordered by the station's bosses to seek medical help and expressed "aggressive" behaviour toward colleagues.

WDBJ's former news chief Dan Dennison said on Wednesday Flanagan had complained of racial discrimination but "all these allegations were deemed to be unfounded".

Flanagan had to be escorted from the building by police when he was fired "because he was not going to leave willingly", he added.

In a 23-page fax sent to ABC News, Flanagan said his anger had been "building steadily" and a recent attack on black church-goers in Charleston, South Carolina, had driven him to "tipping point".

Media playback is unsupported on your device Media caption Alison Parker's boyfriend Chris Hurst shared a photo album of the couple's special moments

Image copyright WDBJ7

Alison Parker

Aged 24, was a reporter for WDBJ7's Mornin' show

Grew up in Martinsville, Virginia and edited her university newspaper

Joined WDBJ7 after internship and said she grew up watching the station

Was dating station anchor Chris Hurst

Adam Ward

Aged 27, was a cameraman for WDBJ7

Went to school in Salem, Virginia, and graduated from Virginia Tech

Described by his employer as committed and a "fine photojournalist"

Was engaged to station producer Melissa Ott

Who were the two journalists?

Image copyright WDBJ7 Image caption Reporter Alison Parker was doing an interview when she was shot and killed live on air

Image copyright Twitter Image caption The Twitter and Facebook accounts of Bryce Williams, Flanagan's on-air name, have been suspended

The woman being interviewed by Ms Parker at the time of the shooting, Vicki Gardner, was also wounded but is in stable condition in hospital

Police recovered two Glock 9 mm pistols from Flanagan, both purchased legally.

Virginia TV shooting