The prisons watchdog revealed on Thursday, October 23, that Carlos Velez had died at the Thamesmead prison on December 4, 2023.
Velez murdered David Martinez after suspecting him of kissing his girlfriend.
He became jealous of the 26-year-old and stabbed him to death at a flat in Leytonstone on March 6, 2019.
Velez was sentenced to life, with a minimum term of 17 years in prison.
Prosecutor Edward Brown KC had told jurors that David was killed “for no good reason at all”.
“He was killed at the hands of this defendant – and was a victim of this defendant’s possessive and short-tempered nature,” he said.
Velez allegedly had a history of violently possessive behaviour, having punched a stranger on the Tube for looking at his girlfriend Ashlly Rondon-Diaz.
He also had an aggressive confrontation with a neighbour, who he suspected of having an interest in Ms Rondon-Diaz, jurors were told.
On the day of the killing, David texted a cousin, writing that Velez was acting “all crazy and was asking if had kissed his girlfriend”.
In another message, he wrote: “I am going to try to go on Friday else I’ll end up dead.”
Ms Rondon-Diaz walked in on Velez attacking David in the kitchen after being alerted by screams, jurors heard.
Mr Martinez suffered multiple knife wounds to the head, shoulder, chest and thigh as well as defensive cuts to his hands, the court heard.
He ran out of the flat but collapsed and died on the pavement.
Velez fled to Portsmouth, where he changed his clothes, jurors heard.
He was stopped by police riding a bicycle beside the M27 outside the Hampshire port.
Velez was aged 23 at the time of his death.
An inquest is set to investigate the circumstances of his death at the Thamesmead prison.
