"We wanted to celebrate Jonny's life one last time," a former student said. "He was such a happy person. I'm sure he would have been glad that looked back on his life."
Several young people at the event at Alexanderplatz in the middle of the city, wore t-shirts with Jonny K.'s picture on them.
No speeches were made at the event, in keeping with Buddhist custom - Jonny's K.'s mother was brought up in Thailand, and both he and his sisters were brought up as Buddhists. A monk did speak a few words during the private service attended by Jonny's K.'s parents and siblings, and around 60 invited guests.
The friends who tried to help Jonny K. but were caught in a fight with his attackers also attended the service.
Berlin Mayor Klaus Wowereit and the Berlin state Justice Minister Thomas Heilmann also attended the private service. "I am here to express my condolences and sympathy with the family," Wowereit told reporters afterwards.
Heilmann said the crime cast a shadow on Berlin. "We as politicians also have to do all we can to investigate this crime," he said.
A 21-year-old man has been arrested in connection with the attack, while police were this week searching for a 19-year-old amateur boxer named only as Onur U.
The Bild newspaper reported on Monday that one of its reporters investigating the story had met Onur U. in a café in Istanbul, Turkey on Saturday. Describing him as a "failed amateur boxer with a Turkish and a German passport," the paper said he was planning to return to Germany to face questioning next week.
"Yes, I was there but I only hit the other guy," he told the paper. "With my fists. I don't know what was happening to the one on the ground. I would never kick someone lying on the ground. That's a question of honour for me."
He also said that the two men previously questioned and released, who reportedly told the police about Onur. U.'s involvement did so to deflect the blame from themselves. "They obviously agreed the story between themselves. They want to put the blame on me," he told the paper.
He also denied that he had fled the country following the killing. "That's not true," he said. "My father had an appointment here about some property. I didn't want to let him come here alone."
German authorities have not yet applied to deport Onur U., and would not say whether an international arrest warrant has been issued.
Melih Y. was arrested last week in connection with the killing, but has been released on bail.
A judge said that he admitted to kicking Jonny K., had agreed to cooperate fully with the investigation, and that there was no likelihood that he would flee. State prosecutors immediately appealed against the decision.