A gunman who killed five people in Plymouth before pulling the trigger on himself in the UK's worst mass shooting since 2012 has been named locally as Jake Davison. 

The suspected killer, whose victims included a child under 10, was a self proclaimed 'incel' according to videos posted on his YouTube channel. 

In the videos, the 23-year-old apprentice crane operator claimed to be "defeated by life", blaming his problems on his lack of girlfriend. 

He also makes references to being an "incel" on the channel as well as the "black pill" philosophy subscribed to by the subculture. 

READ MORE: Plymouth suspect said he was 'defeated by life' in last video before shooting

But what exactly does 'incel' mean? 

What is an 'incel'?

An incel in an abbreviation for "involuntary celibate" which is an online subculture group of people who state they are unable to find a romantic partner despite desiring one. 

Online incel forums are often underlined by discussions of resentment and hatred, mysogyny, misanthropy (contempt for the human species), and racism. 

They also frequently include endorsements of violence against women, with incel culture having been described as "part of the online male supremacist ecosystem". 

There have been numerous cases in which mass murderers have claimed to be part of incel culture, with violence linked to the subculture resulting in the deaths of up to 50 people in the US and Canada.  

Examples include Elliott Rodger, who killed six people in America after publishing a 141-page document detailing his intense hatred of women. 

The killer inspired others in the incel community: in 2018, Alek Minassian posted on Facebook: "The Incel Rebellion has already begun… All hail the Supreme Gentleman Elliot Rodger!"

He then proceeded to kill ten people by driving a van into a crowded street in Toronto. 

What is the 'blackpill' philosophy?

The black pill philosophy refers to a set of commonly held beliefs among the incel community, which has been described as a "profoundly sexist ideology" that "amounts to a fundamental rejection of women's sexual emancipation, labeling women shallow, cruel creatures who will choose only the most attractive men if given the choice". 

The belief also subscribes to the idea that success with the opposite sex is determined by genetics at birth. 

People who to have "taken the black pill" believe they are a hopeless case who will never have any success romantically or sexually.

Suspected Plymouth shooter Jake Davison claimed he had been "consuming a black pill overdose" in an online comment. 

On the matter of Davison's comments posted on his YouTube channel, a YouTube spokesperson said: "Our hearts go out to those affected by this terrible incident. We have strict policies to ensure our platform is not used to incite violence.

"In addition, we also have long standing policies that prohibit those responsible for attacks like these from having a YouTube channel and have since terminated their channel from our platform."

His channel has now been deleted due to content violating YouTube's offline behaviour policy.