A Bulgarian former army officer shot dead three members of a Roma family who lived next door to him before killing himself, police say.
A fourth member of the family was seriously injured in the attack late on Monday evening.
All the victims were adults aged in their 20s, with six children who were present reportedly unharmed.
The shooting happened in a mainly Roma suburb of the capital, Sofia. The motivation was not immediately clear.
Bulgaria's 700,000-strong Roma minority are often subject to attacks and discrimination.
However, Reuters news agency reported witnesses and police as saying that the 67-year-old assailant had been irritated by the smell of burning tyres coming from his neighbours' courtyard.
Police were deployed to the scene amid fears of revenge attacks.