A man killed his baby stepson while "full of rage" following an argument with his ex-girlfriend, a court has heard.
Thomas Morgan is accused of inflicting fatal injuries on Jensen-Lee Dougal when he shook him at the family home in Swansea.
The 29-year-old denies murder and inflicting serious injuries on the child.
Swansea Crown Court heard the five-month-old suffered catastrophic brain damage, numerous fractures, and extensive retinal bleeding to both of his eyes.
Morgan was in a relationship with Jensen-Lee's mother, Jordan Dougal, and was treated as the baby's stepfather, the jury was told.
But he "seriously abused the trust placed in him" when left with the baby on 30 March, 2024, said Caroline Rees KC, prosecuting.
She said Morgan had argued with Georgia Griffiths, his former partner, on the day the baby was shaken.
In an angry exchange of messages, he called his ex names like "stinking rat" and "stinking little dog", the jury heard.
Ms Rees said: "It is clear that this abusive exchange had flipped some kind of switch in Thomas Morgan.
"By the time he was alone with Jenson-Lee, he was angry and aggressive and in no state of mind to be caring for a young baby on his own."
Ms Dougal, who was at work, received a call from Morgan in which he told her the baby was choking and had stopped breathing, the court heard.
Morgan fled the house with the baby, before a neighbour performed CPR on the child and called an ambulance, jurors were told.
Read more from Sky News:
Trump warns 'you'll find out' - when asked how far he'll go to take Greenland
China's controversial 'super' embassy in London approved
In hospital, the baby was found to have a "devastating" brain injury. He was taken off life support the following day.
Morgan, from Gorseinon, Swansea, is charged with murdering Jensen-Lee and three counts of causing him grievous bodily harm with intent.
The 29-year-old denies the charges and says he tried to save the baby after he fell ill in his care.
He said he left Jensen-Lee alone briefly while he fetched a clean babygro, and found him unresponsive with vomit in his mouth.
Ms Rees said: "It is the prosecution case that the defendant, his temper raised and his fuse short after an argument with Georgia Griffiths, must have snapped and shaken Jensen-Lee with such violence that he caused devastating injuries which led to Jensen-Lee's death in his mother's arms at only five months old."
The trial continues.
(c) Sky News 2026: Man killed baby stepson while 'full of rage' after row with ex, court hears
What is in the Chagos Islands deal and why is it controversial?
Woman says she 'begged for pain relief but was told no' - amid national call for birth stories
Prince Harry's privacy case is 'threadbare' and journalist sources were legitimate, lawyer for Mail publisher tells High Court
Trump's Chagos broadside leaves Starmer walking an even thinner tightrope
Will Brooklyn regret launching a grenade at Brand Beckham?
Teenage boy stabbed to death in Surrey woodland
Warning issued after first Asian hornet nest discovered in Wales
Russell Brand appears in court via video link from US to face further rape and sexual assault charges
What it's like to live next to a 25,000-tonne illegal waste dump - with rats everywhere
