Police said it was the second such incident in the area yesterday. The other robbery, which police believed was related, was at the Wilson carpark on Kitchener St at 4.30pm.
A spokeswoman said the "offenders' descriptions and modus operandi" were similar in both incidents.
Lawrence's sister, Lorraine, said her brother was simply trying to do a good deed.
"He just keeps apologising," she said. "He's a good kid, an A student and a youth leader. It's not fair, his intention was to help and he's been traumatised."
Lawrence said the woman who wanted help was European, in her late teens or early 20s.
After following her to the carpark she told him and his mates the lift wasn't working so they took the stairs.
As they passed the 5th floor one man began following them. Another joined the group on the 8th floor and a third was waiting on the 12th.
"I could feel something bad was happening," Lawrence said.
Upon entering the 12th floor the third man locked the door behind them, a fourth appeared and the woman disappeared.
Lawrence described three of the men as black, in their mid-20s and the fourth as "maybe Mexican".
All four were tall and dressed in hoodies.
Lawrence said one grabbed and choked him.
"He was saying 'you're rich, give me your stuff'."
He was strangled for until his vision went blurry and he was close to dropping to his knees.
Lawrence said the man was trying to get his bag, but he didn't want to give it to him.
His laptop contained all his university work from this year, including some to be handed in on Monday.
"I really needed my stuff, I'd been working really hard on my work."
His resistance ended when he was kneed in the stomach.
His friends were unable to step in as they were being held against the wall by the other men.
Lawrence said he and his friends were mocked during the attack. The robbers said it was okay to steal from them because Asians were rich.
Eventually the men left, and another woman arrived who helped the students call the police.
Officers were there within 10 minutes and Lawrence's parents came to take him home.
He refused to go to the hospital, despite extensive bruising on his stomach and neck, but let his sister take him to the doctor for a check-up.
The experience had left him shaken.
"It's in my head, I can't get it out of my head."
Police are seeking CCTV footage from both incidents.
They are advising the public to be wary of a tall, slim, young European woman with blue eyes and brown hair cut in a fringe wanting help with car troubles.
Anyone with information can call the Auckland City Crime Squad on (09) 302 6557 or Crimestoppers, anonymously, on 0800 555 111.
