Police released the CCTV footage showing a group of teenagers and young men entering an U-Bahn train at Schönleinstraße on the U8 line.
In the footage, recorded on Friday evening, the group can be seen laughing among themselves.
According to the police report, the youths had just set fire to the clothes of a homeless man who was sleeping on a bench in the underground station.
The 37-year-old man was not injured, after bystanders came to his rescue.
Police announced though that they had opened an investigation into attempted murder.
On Tuesday a police spokesperson confirmed that six males between the ages of 15 and 21 handed themselves in at various police stations.
A seventh man was detained by plainclothes police officers.
According to a report in die Welt, one of the youths was Libyan, the others were Syrian. All had arrived in Germany since 2014.
“We know who the lead suspect is – it’s the 21 year old,” a police spokesperson told broadcaster RBB.
The case follows the arrest of a Bulgarian man last week, who is suspected on kicking a woman down the stairs at Hermannstraße U-Bahn station.
The 27-year-old was caught after police released CCTV footage of the incident which spread rapidly across the internet due the shocking and apparently random nature of the crime.
Schönleinstraße station is a four stops from Hermannstraße station on the U8 in Berlin’s Neukölln district.
Despite the brutality of the two crimes, the Berlin transport company (BVG) say that violent crime has actually gone down in U-Bahn stations in recent years.
While in 2011, 880 violent incidents were recorded on the capital’s public transport network, in 2015 almost half that number, at 480, were recorded.
“Word has spread that there is CCTV there now,” a BVG spokesperson told the Frankfurter Allgemeine Zeitung.