PC Mia Kerr arrived at 10.12pm – just minutes after the attack began – and discovered Sebastien Belanger, 36, collapsed in Green Dragon Court, below the spot where the attackers’ van crashed into railings on London Bridge.
At first, she protected the scene single-handed armed only with a baton as members of the public gave first aid, the Old Bailey heard.
The Frenchman, who had a deep stab wound to the stomach, appeared to have a “faint pulse” but later became very cold, the officer said.
Ms Kerr was giving evidence to the inquiry into the deaths of the eight people who were killed in the attack on 3 June 2017.
She had been on duty with PC Clint Wallis when they got the call about a van hitting pedestrians, and said she had suspected it may be a terror attack.
When they arrived on the scene, they saw the van crashed into railings at the Barrowboy and Banker pub and a woman was on the floor at the top of the steps by the pub.
They jumped out of the car and PC Clint Wallis went to woman on the floor and told Ms Kerr to go down the steps, the inquiry heard.
Ms Kerr told the inquest she saw a man on the floor who looked “seriously injured”.
“I didn’t want there to be any more casualties,” she said.
She drew her baton to protect the people assisting Mr Belanger and made a radio call at 10.15pm to report the stabbing.
“I was the only officer down there,” she said.
Ms Kerr said she could hear Mr Belanger gasping and told a woman to put him in the recovery position, adding that she could not feel a pulse.
She said she could see a stomach wound and laceration to his cheek, and told the woman to start CPR while she took a plastic bag out of her personal protection kit before helping them.
She used the bag to cover the stomach wound.
She was then joined by another female officer and they both began assisting the woman in giving CPR, while a man held the bag over the wound.
She says there was a discussion of whether there was a pulse.
Darren Laurie, a police medic, arrived on the scene at 10.38pm and took charge.
“I was thankful,” she told the inquest.
A defibrillator was applied but no shock was advised.
Mr Belanger, 36, was then carried up the steps towards waiting ambulances at around 10.45pm.
Gareth Patterson, QC, for the victim’s family, thanked the officer, saying: “It sounds as if you were concerned for your safety throughout but nevertheless carried on with your efforts armed only with a baton.”
Ms Kerr replied: “Yes. Just batons. I was also concerned I was the only officer down there for a while. It felt like forever. I felt I was the person they were looking to for help by myself.
“I only had a year’s service in the response team. It felt like a lot of pressure, looking back on it.”
Mr Patterson highlighted repeated messages referring to casualties in the courtyard, saying it was “obvious” things were going on.
On body worn footage, messages could be heard requesting London Ambulance Service (LAS) be alerted to a man with a stab wound to the abdomen.
Mr Patterson said: “If you had been told there were LAS resources available before then, up on the High Street, presumably you would have discussed getting Sebastien up to those ambulances as quickly as possible?”
Ms Kerr said: “We would have discussed it yes.”
Asked why they did not reach her, she said: “I can only assume that it was because they may have deemed the area too dangerous.”
Mr Patterson said: “We have heard from two LAS witnesses saying they were unaware of all this activity going on below in the courtyard. Were you and the others down there speaking quietly?”
Ms Kerr replied: “I doubt it.”
She added: “Everything was noisy. It was just a lot of noise.”
Ambulance service incident response officer Nicholas Lesslar told the court Mr Belanger’s injuries were “incompatible with life” and another casualty who was breathing and talking needed the ambulance more.
Xavier Thomas, 45, Christine Archibald, 30, Alexandre Pigeard, 26, Sara Zelenak, 21, Kirsty Boden, 28, Mr Belanger, James McMullan, 32, and Ignacio Echeverria, 39, all died in the atrocity before their attackers were shot dead by armed police.