Doctors were unable to save Mark English, 53, from injuries he suffered in the alleged attack in Brisbane's CBD on Monday afternoon.

Mr English, referred to in court documents as Mark Bradley McGrice, was knocked out in the alleged attack, which saw him fall backwards and smash his head into the footpath opposite Central train station about 4pm.

He was operated on at the Royal Brisbane and Women's Hospital overnight but it's understood doctors couldn't stem the bleeding.

It's understood his family had been preparing for the bad news for most of the day.

Morgan Alexander Isles-English, of Teneriffe, broke down in the Brisbane Magistrates Court on Tuesday morning, where he faced a charge of grievous bodily harm over the alleged attack. Early on Wednesday morning, police said the charges would be upgraded to unlawful striking causing death.

In court, Isles-English yelled out "I love you Mum" from within the glass walls of the prisoner dock, sobbing loudly as his lawyer asked for the case to be adjourned.

"I love you too," she mouthed back.

The 25-year-old paced up and down, hands cuffed and decked out in a prison-issue tracksuit, hitting his head against the glass several times before putting his head in his hands and continuing to cry.

The woman believed to be his mother, also clearly emotional, didn't want to speak to media as she left the court.

Isles-English's lawyer, Brendan Beavon, asked for the case to be adjourned and did not have anything to say outside the court either.

The case was adjourned to August 15 but due to the charges being upgraded, Isles-English is now expected back in court on Wednesday.