CHICAGO – Maybe it is the splintering of established drug gangs that has young men grabbing the tools of their trade – handguns – to jockey for position. Or it is that rival gangs, once miles apart in different public housing complexes, suddenly finding themselves sharing the same street corner.

Whatever the reasons, Chicago has seen a spike in its homicide rate – with eight killed and at least 35 wounded in a spasm of gunfire last weekend alone – that has authorities scrambling to put more police on the street and some frightened residents retreating deep into their homes.

To be sure, the violence is far from its historical peak of the early 1990s when Chicago recorded roughly 900 homicides per year. But from Jan. 1 through late May there were 203 homicides, an increase of more than 50 percent over the 134 during the same period in 2011.