From SCPR:
"That was all turned around by the San Francisco shooting, I think," said UC Irvine political scientist Louis DeSipio, "because that raised concerns among those … opposed to large scale unauthorized immigration, and gave them a focus for their concern that the Obama administration was becoming too generous or too inclusive of unauthorized immigrants."

Audio available at http://www.scpr.org/news/2015/07/15/53140/debate-over-immigration-program-heats-up-after-san/.