A MAN who allegedly killed his father in a one-punch attack in Brisbane’s CBD has appeared in court charged with unlawful striking causing death.

Police allege victim Mark English was walking along Ann Str with a woman when his 25-year-old son, Morgan Isles-English, approached him about 4pm Monday.

The pair had a brief verbal exchange before Isles-English allegedly hit his father in the mouth, causing him to fall back and hit his head on the ground, knocking him unconscious.

Mr English died in hospital yesterday and his son’s charge was upgraded from grievous bodily harm to unlawful striking causing death, which carries a maximum sentence of life behind bars.

Isles-English appeared briefly in the dock at the Brisbane Magistrates Court this morning.

He told his mum he loved her before he was taken back down to the watch house.

There was no application for bail.

The case was adjourned to August and he will undergo a court-ordered mental health check before that time.

OVERNIGHT: An estranged son knocked his father unconscious in a fatal one-punch attack in broad daylight after randomly spotting him walking down the street in Brisbane’s CBD, police will allege.

Morgan Alexander Isles-English last night had his charge upgraded to unlawful striking causing death after his father Mark, 53, succumbed to his injuries in the Royal Brisbane and Women’s Hospital.

Hours earlier, a distressed Isles-English broke down and sobbed in the dock when he fronted Brisbane Magistrates Court on one count of grievous bodily harm over the ­alleged incident on Monday.

In emotional scenes, the 25-year-old paced back and forth in the glass-walled ­prisoner’s dock, crying out to a woman in the public gallery that “I love you, Mum” and asking whether “he was awake”.

Defence lawyer Brendan Beavon, from Russo Lawyers, did not make an application for bail on his client’s behalf and requested the matter be adjourned to next month.

No details of the alleged attack were read out in court but it is believed Isles-English was in a bar when he spotted his father Mark McGrice – also known as Mark English – walking down the street with his partner about 4pm on Monday.

There were reports that the pair had not seen each other for four years.

Police allege the pair had a “brief verbal exchange” on Ann St before Isles-English hit his father in the mouth.

The father fell back and struck his head on the ground, losing consciousness.

Police said the Ashmore man’s partner, who was not physically injured, performed first aid on him before he was rushed to the RBWH with life-threatening injuries.

Shortly before 5pm yes­terday, Queensland police ­released a statement confirming that the 53-year-old had died.

Mr English, who was born in Victoria, described himself on social media as a chef who was a “jackaroo of all trades, master of one” and wrote that he was “living life large with the most wonderful life partner your soul could find”.

Isles-English is expected to re-appear in court today on the upgraded charge, which carries a maximum penalty of life imprisonment.

The accused’s mother ­declined to speak to media as she left the courthouse ­yesterday.