A chilling video shows Tunisia gunman, Seifeddine Rezgui, shortly after his deadly rampage on Sousse beach. Twitter

A chilling 55-second video has emerged showing the Tunisia gunman shortly after his deadly rampage on the Sousse beach.

In the short video clip, gunman Seifeddine Rezgui, 23, can be seen running along the beach dressed in black.

He can also be seen carrying the assault rifle that he used to carry out the shootings that resulted in the deaths of nearly 38 tourists, including at least 15 Britons.

The video was reportedly shot from a balcony soon after Rezgui opened fire on tourists, reported Sky News.

According to witnesses, Rezgui was "very, very calm" as he opened fire on tourists and other beachgoers.

Rezgui engaged in the 25-minute deadly killing spree at the Riu Imperial Marhaba Hotel in Port el Kantaoui, on the outskirts of Sousse south of the capital Tunis, on 26 June.

"The shooter had his weapon concealed inside a sun umbrella - he basically came here, went into the water and washed," said Sky's Chief Correspondent Stuart Ramsay.

"Then he came out, he got his gun out. He was very, very calm - he then attacked one woman shooting her dead immediately.

"He walked past a number of Tunisians who said to him 'why are you killing these people, why are you killing these people?' He basically sneered at them and said 'well I'm not killing you' and basically walked on past them."

A number of builders working on top of buildings reportedly threw bags of cement and bricks attempting to hit Rezgui who was eventually shot down by police.

Meanwhile, David Cameron said in a statement on Friday (26 June): "These terrorists murdered them because the terrorists oppose people and countries who stand for peace, tolerance and democracy wherever they are in the world. But these terrorists will not succeed."

Questions are now being raised on whether the police acted on time and whether security was sufficient at the scene.

"The security system did not work properly to avoid that slaughter," Sami Tounsi, trade manager for the Tunisian tourist offices in London told The Sunday Times.

Tunisian Interior minister Mohamed Najem Gharsalli (2R) arrives at the site of the shooting attack on the beach in front of the Riu Imperial Marhaba Hotel in Port el Kantaoui, on the outskirts of Sousse south of the capital Tunis, on June 28, 2015. The Islamic State (Isis) group claimed responsibility on June 27 for the massacre in the seaside resort that killed nearly 40 people, most of them British tourists, in the worst attack in the country's recent history. Getty Images