Barron Trump told British authorities his heart was racing as he witnessed a “very close” female friend and alleged rape victim get beat up by her ex-boyfriend on a FaceTime call.

President Trump’s then-18-year-old son frantically alerted police in London after realizing his friend was embroiled in a violent dust-up with her former beau, Matvei Rumianstev, early last year, Metro reported.

Prosecutors on Thursday detailed an email exchange the first son had with police in the wake of the alleged attack when they asked if Barron would consider giving a witness statement in the criminal case against the suspect.

In his reply, Barron noted that what he saw unfold on the call was “very brief indeed but indeed prevalent” — acknowledging that the scary video call left him “racing with adrenaline.”

“I made two of my friends call the Met Police in the UK, even though they are in the US,” he wrote in an email, which was shown in Snaresbrook Crown Court during the alleged attacker’s trial.

“As per evidence I do not have any, I was told by the victim who I am very close with that this individual was giving her difficulty for a long time.”

It wasn’t immediately clear how Barron knew the young woman or how long they’d been friends before the alleged attack.

His involvement in the case exploded into public view only after audio of a call to emergency operators was played in court on Wednesday.

The first son, who was in the US at the time, recalled calling his friend but noted that he “didn’t expect her to pick up due to the time difference.”

“The phone was answered, but not by her to my dismay,” his email read.

“The individual who answered was a shirtless man with darkish hair. This view lasted maybe one second … then the view flipped to the victim.”

Rumianstev, who is on trial for raping and assaulting the victim, allegedly started battering his ex-girlfriend because he was jealous of her friendship with the president’s son, the court previously heard.

After witnessing the alleged assault, Barron quickly called for help, telling dispatchers: “I just got a call from a girl I know. She’s getting beaten up.”

“It’s really an emergency, please. I got a call from her with a guy beating her up,” he added after giving his friend’s address and urging them to head there.

When officers arrived at the scene, the woman allegedly told them: “I am friends with Barron Trump, Donald Trump’s son.”

The alleged victim then called Barron back so police could confirm her story, the court heard.

“I called you guys; that was the best thing I could do,” Barron told cops, according to the audio.

“I wasn’t going to call back and threaten things to him because that would just make the situation worse.”

The White House hasn’t addressed Barron’s involvement in the ongoing case.