Shocking CCTV footage shows the man identified as Mikhail Stepanov, 44, approaching a parked car with a gun and firing at the driver.
The man inside the car, lawyer Dmitry Vaskov, 35, can be seen quickly speeding off camera, crashing through some closed gates.
Reports said he died moments afterwards because one of the bullets hit his heart, causing him smash into some nearby dustbins on the street in the city of Ulan-Ude, south-eastern Russia.
Lawyer Vaskov was reportedly specialised in tackling complicated criminal cases and it has been confirmed that he was helping Stepanov, a local businessman, on several cases.
However local media reporting the incident claimed the victim was also allegedly involved in an illegal enterprise trafficking jade with Stepanov before their relationship apparently turned sour.
One week ago, police found 8 kilogrammes (17.6 lbs) of jade, a precious stone, in one of the local hotels.
Investigative teams believe that Stepanov owned the jade stones, the price of which was estimated at around 50 million RUB (608,500 GBP).
It has also been suggested that Stepanov sought to kill Vaskov over the fact that the jade turned up in police hands.
Stepanov is now under arrest, although there are conflicting reports as to how he was seized.
Some media outlets claim that police found him in his apartment, after he was identified from the CCTV footage.
Other versions report that the man came to police of his own accord, and confessed to the murder.
The case is still ongoing and officers are still investigating.