At least six people, including the shooter, were killed in a mass shooting at a fresh food market in Bangkok, Thailand on Monday. Four of those who died were security guards working at the market, according to reports.

News agency Reuters reported that the gunman opened fire in the busy Or Tor Kor Market and later took his own life. The Erawan Emergency Medical Centre, which monitors hospitals in Bangkok, confirmed that the victims include four security guards, a woman, and the shooter.

Or Tor Kor Market is located close to the popular Chatuchak market, a major tourist spot in the Thai capital.

“Police are investigating the motive. So far it’s a mass shooting,” said Worapat Sukthai, deputy police chief of Bangkok’s Bang Sue district, speaking to AFP. He added that officials are also checking “for any possible link” between the attack and ongoing border clashes between Thailand and Cambodia.