On Edit: There were three shootings - the first two took place on consecutive days in 2018, and are connected by ballistics; the third took place on around 1:30 am on March 19. I'm not sure what you mean by the first and the second. The first two (in 2018) are absolutely connected by CPD as being the same shooter based on surveillance camera video and ballistics.
The similarities are 1) the location - these three killings each took place very close to each other; 2) a lone shooter on foot wearing a ski mask; 3) seemingly completely random.
Chicago has 700 murders a year, but most of those are gang related and/or related to some secondary crime (i.e., a robbery). Random shootings are relatively rare, in Chicago as elsewhere. This doesn't mean that random people don't get hit by gunfire, but for a gunman to approach and shoot specific people with no seeming motive is rare everywhere, including in Chicago. I understand that it's common to slander Chicago as some violent hellhole, especially among the right wing, and Chicago certainly has its problems, but random Son of Sam type shootings are not, despite what Hannity might tell you, common at all. This is a top-level news story in Chicago.
The larger neighborhood of Rogers Park certainly has some gang-related violence, but I don't know if a group of Loyola students has ever been shot at like this in recent memory.
Now for the differences: in the previous two shootings, the killer targeted a middle-aged to older man, in both cases, alone. The killer in this case targeted a group of students, including women (the victim is a woman).