Real estate agents arrive at a brokers tour showing a house for sale in San Rafael, California.

The pace of U.S. home price gains cooled off in May, coming in below consensus estimates, as regional patterns were seen shifting, according to a monthly report.

The S&P CoreLogic Case-Shiller 20-City Composite index rose 5.2 percent year over year, versus expectations for a reading of 5.7 percent. That marked a sequential slowdown from April's 5.4 percent increase.