At least four people were killed after a shooter opened fire at an annual food festival in northern California, The Guardian reports.

A gunman opened fire on Sunday, July 28 evening on the last day of the Gilroy garlic festival, killing at least three people, before being shot dead by police. At least 15 people were injured.

The Gilroy police chief, Scot Smithee, said some witnesses had reported that there may have been a second suspect, but authorities were not sure that second individual was engaged in the shooting.

Authorities did not release further information on the identity of the suspect or the victims. The police chief said the motive behind the killings remained unclear.

“This is one of those press conferences that you never want to give in your community. It’s sort of a nightmare that you hope to never have to live in reality, but we find ourselves in the circumstances where we have to live it today,” a tearful Smithee said.

Images and videos posted to social media showed a confusing scene.