That Wikipedia article doesn't draw any connection between modern policing and the slave patrols, though it points out the well documented connections between militia efforts and enforcing slavery. Similar institutions date to the Romans[1], which would suggest that slave catchers and the like may not be directly linked to our idea of a municipal police department.
The second source seem to support the connection, but doesn't document any actual institutional connections. It relies on similarity, and bald assertion. The existence of overlap between the KKK and local law enforcement is evidence that policing in the US is racist. It isn't actually evidence that the institutions of policing were descended from slave patrols.
I'm not a huge expert on criminal justice, but my degree is history, and these kinds of assertions seem to ignore the parallel developments in NYC, Boston, and other Yankee cities in policing and crime solving that established our idea of a municipal police department. That such departments may have been racist isn't a surprise, virtually every institution in 1880 was, but they were in states that did not practice slavery(abolished in 1799 in NY) and as a result had no institutional history of enforcing it.
Consider that Federal Marshals were so reluctant to enforce laws on the return of escaped slaves that it took an act of congress, with severe financial penalties, to get them to actually enforce the "property claims" of southerners.
1 - http://www.bbc.co.uk/history/ancient/romans/slavery_01.shtml