Islamic State said on Saturday that the married couple who killed 14 people in a mass shooting in Southern California were its followers, and FBI agents raided a home apparently belonging to a friend of the husband, reports.

Islamic State’s claim came in an online audio broadcast three days after U.S.-born Syed Rizwan Farook, 28, and his Pakistani wife Tashfeen Malik, 29, opened fire with assault rifles on a holiday party for civil servants in San Bernardino, 60 miles (100 km) east of Los Angeles.

The pair, who had left their six-month-old baby daughter with relatives, were killed two hours later in a shootout with police SWAT team members.

Federal agents tore through a garage door to search a house in Riverside, a few miles (km) southwest of San Bernardino, on a street where neighbors said Farook once lived.

An FBI spokeswoman confirmed agents made a “precautionary tactical entry” while serving a federal search warrant, but she declined to give details.