Global travel company Airbnb announced on Saturday that it would ban “party houses” after a mass shooting at a California home rented through the firm that left five people dead.

In a series of tweets, CEO Brian Chesky tweeted, “Starting today, we are banning ‘party houses’ and we are redoubling our efforts to combat unauthorized parties and get rid of abusive host and guest conduct, including conduct that leads to the terrible events we saw in Orinda…”.

We must do better, and we will. This is unacceptable,” he further posted.

Police are still searching for the shooter who opened fire on Thursday night at the costume party, which authorities said that it was attended by more than 100 people at the house in Orinda, less than 20 miles (30 km) east of San Francisco.

Late on Friday, Contra Costa Sheriff’s Office said that the death toll climbed to five after a 19-year-old victim succumbed to her injuries at a hospital.

The company was expanding manual screening of “high-risk reservations” flagged by its risk detection technology, and was creating a house party “rapid response team,” Chesky added, without elaborating.

In his tweets on Saturday, Chesky added that Airbnb would create a dedicated “party house” rapid response team and expand manual screening of high-risk reservations, the BBC reported.

In response to the mass shooting, California Governor Gavin Newsom called for Congress to pass gun control legislation.

Authorities identified the victims who died as Oshiana Tompkins, 19; Tiyon Farley, 22; Omar Taylor, 24; Ramon Hill Jr., 23; and Javin County, 29. Several other people were wounded, police said, without giving an exact number.

Some of the victims transported themselves to the hospital in the chaos after the shooting which sent young people, including some in Halloween costumes, fleeing from the scene.