Poignant moment a lone cop kneels at Beau's grave while Joe Biden gives his inauguration address in DC

An unidentified man in a blue uniform was pictured kneeling by the grave of Beau Biden while his father Joe delivered his inaugural address as 46th President of the United States.

The mourner, who appears to be wearing a police officer's uniform, kept his head bowed and his hands clasped as he held vigil alone at St. Joseph on the Brandywine church in Greenville, Delaware.

According to Delaware News Journal, who first published the picture, the man did not speak and remained at the grave even after Biden had stopped speaking.

It is not certain if he had been stationed to protect the grave during the ceremony - in light of the recent violence from angered Trump supporters - or if he had made the decision to stand guard himself.

An unidentified man in a blue uniform was pictured kneeling by the grave of Beau Biden on Wednesday while his father Joe delivered his inaugural address as 46th President

 The man waited by the graveside throughout ceremony. Pictured, Joe Biden is sworn in as the 46th president of the United States by Chief Justice John Roberts as Jill Biden holds the bible

Beau, pictured left, died of cancer in 2015 at the age of 46

The News Journal reporter said they did not approach the man to identify him out of respect.

The only other people in the cemetery were some maintenance workers.

Just the evening before his inauguration, Joe Biden spoke of the loss of Beau, who died of cancer in 2015 at age 46.

The 78-year-old became emotional as he said goodbye to his home state of Delaware on Tuesday night, stating that it should be Beau that was being introduced as the President-elect. 

He delivered the speech eulogizing his dead son from the Major Joseph R. 'Beau' Biden III National Guard /Reserve Center at the New Castle Airport just before he set off for D.C. 

Biden became teary on Tuesday night as he spoke of Beau during his farewell to Delaware

Items left by visitors decorate the grave of Beau Biden just after Biden's win on November 8

'Ladies and gentlemen, I only have one regret,' said Biden. 'He's not here, because we should be introducing him as president.'

'When I die, Delaware will be written on my heart and the hearts of all of the Bidens,' Biden continued. 

'We love you all, you've been there for us in the good and the bad, you never walked away. 

'And I am proud - proud, proud, proud to be a son of Delaware and I am even more proud to be standing here doing this from the Major Beau Biden facility.' 

Beau was a member of the Delaware National Guard and had served as Delaware attorney general from 2006 until 2015 but his father claims he had ideas at a run for higher office.

Joe has previously cited his grief over the loss of Beau as the reason he did not run for the presidency in the 2016 election.

Before his death, Beau had encouraged his father to run for president in 2016, instead of letting Hillary Clinton become the heir to President Barack Obama's legacy.

Yet after Beau died, Joe sat out the 2016 race, which saw Clinton lose to Republican President Donald Trump.

Biden decided to run for president in 2020 after watching Trump handle the racial violence in Charlottesville in 2017.

In the lead up to his election win, supporters often left small accessories from Biden's campaign on Beau's grave in tribute. 

Joe Biden visiting his son Beau's grave on the day after his victory was declared in November