A woman was killed and six others were injured in San Diego, United States, on Sunday after a gunman opened fire near a pool at an apartment complex, reported The San Diego Union-Tribune. The assailant, identified as 49-year-old Peter Selis, was later shot dead by the police. The victims are believed to be in critical condition.

The incident took place on Sunday evening when the victims were attending a birthday party near the pool in the University City community in the Californian city. The person whose birthday was being celebrated is also believed to have been shot in the incident. Eyewitnesses said the shooter was drinking beer and near left his chair as he fired at people, CBS News 8 reported.

The gunman was a resident at the complex, Chief of the San Diego Police Shelley Zimmerman said, adding that they had not ascertained a motive yet. “Our hearts go out to all the victims, their families and anyone who witnessed this tragic event,” she said.

Several incidents of gun violence are reported in the US every year. On April 16, nine people were injured in a shooting in an Ohio nightclub. In March, one person was killed and 15 others injured after a gunman opened fire in a club in Cincinnati. That incident was also triggered by an altercation.