Police have retrieved CCTV footage taken from Pulse nightclub on June 12, when Omar Mateen went on a deadly rampage, killing 49 people and injuring 53 others. Security cameras in the Orlando gay club captured the entire ordeal, as innocent victims were brutally killed, one-by-one.

Investigators said the footage reveals how the 29-year-old killer embarked on a rampage in cold-blood. They have not released the CCTV footage.

As the investigation into the massacre continues, authorities have been searching Mateen's activity on social media. The Orlando Sentinel reports that On 15 June, a letter from the Senate Homeland Security Committee to Facebook, revealed that at least five Facebook accounts were found to be associated with the American-born Muslim.

In a series of posts written before and during the attack he wrote: "The real Muslims will never accept the filthy ways of the west." "America and Russia stop bombing the Islamic state," Mateen wrote, according to the letter. In a final chilling post he, warned "in the next few days you will see attacks from the Islamic state in the usa."

Despite his remarks, CIA director John Brennan said the agency has found no direct connection between the gunman and any foreign terrorist organisation, suggesting he may have been operating as a lone wolf.

"As we have seen in Orlando, San Bernardino and elsewhere, ISIL is attempting to inspire attacks by sympathisers who have no direct links to the group," Mr Brennan told the Senate Intelligence Committee.

"Last month, for example, a senior ISIL figure publicly urged the group's followers to conduct attacks in their home countries if they were unable to travel to Syria and Iraq."

While the FBI continues to gather evidence as they piece together Mateen's activities leading up to the massacre, the first burials of the victims are due to take place, Mirror Online reports.

President Barack Obama is expected to meet with victims' families and first responders today (16 June). As the latest attack – the deadliest shooting in US history – put the spotlight on US gun control, the president said those defending the rights of individuals to have access to assault weapons should meet the families of those killed in the Orlando massacre.