Update: Latest details released by the police suggest the shooting was pre-meditated, and motivated by a long-term feud between two Albanian families.  The alleged perpetrator is believed to have traveled to Vienna especially to carry out the revenge killing.  The meeting on the tram was no accident, according to police sources.

A third person was also injured, but less seriously, according to a police report.  The 19-year-old woman, who was thought to be an innocent bystander, had been entering the tram when she was hit in the leg by a stray bullet.

The shooting occurred after an argument among four men on the tram, which was at the Johnstrasse stop of the 49 tram line.

As two of the men were leaving the tram, one of the other men fired several shots at them.  The first victim, a 28-year-old man, was hit by several bullets in the upper body.  He died in hospital during the night despite several hours of emergency surgery.

The second victim, the 25-year-old brother to the dead man, was also hit in the upper body by several bullets, and was reported to be in a serious condition in hospital, where he remains in intensive care.

The attacker and his accomplice were last seen running away from the incident in the direction of the city centre.

Police have released this surveillance photo of the suspect, who should not be approached.

Police found several 9 mm cartridges, but a weapon was not recovered at the scene of the crime.  Forensic investigation has begun, and police are examining footage from surveillance cameras from the tram.

Any potential witnesses are being asked to contact the police under the Vienna telephone number 311310/33800.