The police officer accused of murdering ex-footballer Dalian Atkinson has told a court he was "terrified" he was going to die during the encounter.
Benjamin Monk is accused of using unlawful and unreasonable force when he fired a Taser at the former Aston Villa star for 33 seconds before kicking him in the head.
Monk, a constable with West Mercia Police, has denied murder and manslaughter and gave evidence for the first time at Birmingham Crown Court on Wednesday.
A jury has heard how Monk deployed three Taser cartridges before Mr Atkinson was handcuffed near his father's home in Meadow Close in Telford, Shropshire, in the early hours of August 15, 2016. The former footballer later died in hospital.
Monk told the jury how he felt "a big relief" when Mr Atkinson was floored after being tasered the third time.
He added that the first two Taser strikes had been ineffective.
Monk claims Mr Atkinson told him, during the encounter that "you can put 100,000 volts through me, I'm the messiah - your Taser won't work and now I'm going to take you to the gates of hell".
Asked how he felt after the second Taser strike failed, the officer of then 14 years' service, said: "I remember just thinking, 'we're done for'."
When asked by his barrister Patrick Gibbs QC what he did next, Monk replied: "Ran for my life - we ran away."
He told the jurors it was something he had never done before in his entire career.
The 43-year-old said: "He (Mr Atkinson) was very, very scary.
"And the device which I thought might work for me, hadn't worked and I was terrified."
Monk and junior colleague PC Mary Ellen Bettley-Smith, with whom he was in a relationship at the time, had backed away from Mr Atkinson in the residential close while waiting for more officers to arrive.
By this time, Mr Atkinson had smashed the glass in the front door of the property belonging to his father.
Both officers had been sent to the address after members of the public called 999 reporting a concern for the welfare of the elderly occupant.
During the course of the first two failed Taser strikes, Bettley-Smith called for back-up, activating her emergency button, calling all available units to the location.
Monk then described hearing one of the back-up units radioing to tell the pair they were still "six minutes" away.
Monk said when he tasered Mr Atkinson a third time, the ex-footballer "stopped moving towards me and seemed to stop where he was".
He added: "He fell to the floor.
"I know he timbered, but I can't say if it was from standing."
Asked how he felt in that moment, Monk replied: "If this cartridge didn't work, Ellie (Bettley-Smith), me, the gentleman inside the house, were potentially done for - so the fact it worked it was a big relief."
Monk said he had "very much so" considered running from Mr Atkinson, leading him away from the close, but said: "We had to protect the man inside the house."
The constable said Mr Atkinson started "plucking" at his clothing while on the ground, which the constable felt was an attempt to free the Taser's electricity barbs, in order to get back up.
At that point, he recalled Bettley-Smith coming across and "she delivered some baton strikes to the lower area of Mr Atkinson's legs".
Monk said Mr Atkinson was then trying to get into a "position where he's about to right himself".
Asked what he did, Monk told the court: "I kicked him."
The court has already heard evidence that Monk's boot connected with Mr Atkinson's head, but the officer said that at the time he believed he had kicked the 48-year-old "in the shoulder".
Monk also said the force of the kick was "about a four" out of 10 on a sliding scale.
The constable said: "I wanted Mr Atkinson to stop getting up because I thought if he's going to get up, we were going to die."
The court has previously heard that Taser-trained Monk had depressed the weapon's trigger for 33 seconds during the third strike.
When asked if he had been conscious of doing so in evidence, he replied: "Absolutely not. Absolutely not."
Mr Atkinson died about 70 minutes after the incident, with Monk telling jurors that when he found out the news from an inspector back at the police station, it left him "devastated".
Bettley-Smith, 31, is also on trial, and denies a charge of assault occasioning actual bodily harm, by using her force-issue extendable baton.
The trial continues.