Mass shooting in coastal city of Half Moon Bay

San Mateo Sheriffs search a downtown area the day after a mass shooting at two locations in the coastal city of Half Moon Bay, California, Tuesday.

HALF MOON BAY, Calif. — A deadly rampage by a 67-year-old suspect in Northern California was likely an act of workplace violence, authorities said on Tuesday, offering fresh details about the second in back-to-back mass shootings that killed 18 people and horrified the nation.

In two separate shootings within three days, 11 people were killed at a Los Angeles-area dance hall and seven others were murdered at two farms in the seaside town of Half Moon Bay near San Francisco.