Wisconsin – A gunman killed six people and left three others critically wounded in an attack on worshippers at a Sikh Gurudwara in a Wisconsin suburb Sunday before being shot by a police officer.

At least 20 people were also injured when at least one shooter opened fire indiscriminately. Greenfield Police Chief Bradley Wentlandt said four people were gunned down inside the Gurudwara while three including the shooter died outside the shrine. The identity of the victims were immediately not known.

Police said they have not yet identified if there was any additional shooter.