I disagree. I expect Dr. Rahman is very familiar with the actions of organized crime and other criminals.
It's a variant on the long tradition of symbolic asassinations. Consider the man who recently shot a CEO of a US health insurance company, on the street in NY. He wrote a message on the bullets. He didn't care about the man, he just did it because he wanted to bring attention, through the news media coverage of the murder, to the issue of the health care system. It was entirely symbolic, has nothing to do with the actual man.
Charles Manson had his followers select a random house and murder all the occupants, writing something in blood on the walls, believing that it would ignite a race war. ie the murders had nothing to do with the individuals but were entirely symbolic and so that the message would be delivered through the news media coverage. Interestingly, it didn't work - no one understood the message until Manson explained it.
Organized crime do this as well, since they can't call police/government to intervene in their disputes, or use ordinary advertising channels. The mafia has always governed by violence. But, traditionally, they would just break someone's legs or set fire to their home, and rely on word of mouth about the open secret. IMO, with the advent of mass communication, and competition in the drug trade, the violence has escalated...
The epitome of this is the wars of the Mexican drug cartels, when they are in intense competition with each other, as well as authorities. Around 2010 the brutality escalated to the level where a new gang would advertise that they'd moved into an area by killing a dozen innocent people and leaving all their bodies in an abandoned vehicle, or tossing their heads in a busy venue.
People often believe these crimes have something to do with anger or revenge or sociopathy, but not at all: they're simply warnings "don't mess with us because we'll stop at nothing". They are completely symbolic, and they target innocent people because they're just easier to kill, unlike other gang members who are on guard.
The crimes are completely outrageous precisely so that the message isn't confused with other theories about them being personal.
JMO
ETA In this and potentially other unsolved cases, the message might have been directed to only a few people, rather than the general public. The name of the victim, the blue envelope and the name Paul could add up to a highly direct message to some people in the criminal underworld.