Disturbing new video shows the moment a big-hearted activist and talented poet was randomly stabbed to death in front of his girlfriend – who desperately tried to get help in the aftermath of the harrowing attack in Brooklyn.

Ryan Carson, 32, and his girlfriend can be seen sitting on a bus stop bench in Bedford-Stuyvesant and speaking with his girlfriend as the two made their way home from a wedding on Long Island just before 4 a.m. on Monday, according to the surveillance footage.

Wearing a gray suit, Carson and the young woman, dressed in a blue, sleeveless gown, get up and begin to walk down the block, in the same direction as a man in a dark colored sweatshirt who had just strolled past the pair at the B38 bus stop, with his hood up over his head and his hands in his pockets.

Just feet ahead of them, the stranger begins kicking scooters parked near the curb for no apparent reason, the footage – obtained by The Post on Tuesday – shows.

Suddenly, the unhinged man turns to Carson and seethes: “What the f–k are you looking at?”

The beloved community activist – who replied that he wasn’t looking at anything – then stepped between his girlfriend and the irate stranger, who began to advance on the couple.

“I’ll kill you!” the maniac threatens as Carson pleads with him to “Chill! Chill!” and holds up his hand.

But the attacker pursues Carson, pulling a knife, as the victim’s girlfriend – running up behind them – is heard frantically yelling “Please, please, please!”

As he runs, Carson tumbles over the bench the couple had earlier been sitting on. The assailant then grabs his jacket and knocks him onto the ground, savagely stabbing him multiple times in the chest as the victim’s girlfriend catches up to them.

He then walks away as Carson lies curled up on the ground, before returning and approaching the terrified woman, who raises her hand to stop him.

The sicko spits on her – while still clutching the knife – before kicking Carson’s mortally wounded body and storming away.