The officer was wounded but "returned fire, and that shooter was put down," said Bradley Wentlandt, the police chief in nearby Greenfield, who briefed reporters. Investigators who picked through the building afterward found four bodies inside the temple and two other victims outside, plus the gunman, Wentlandt said.
The shooting occurred around 11 a.m. Sunday morning at a temple in Oak Creek, south of Milwaukee along Lake Michigan.
Witnesses told local NBC News affiliate TMJ4 that a shooter opened fire inside the temple during Sunday morning worship.
Authorities from several agencies, including the FBI, are also on the scene, CBS News reported.
A police officer who responded to a 911 call was shot multiple times by the shooter, CBS News reported, but returned fire, Greenfield Police Chief Brad Wentlandt said.
The officer, who killed the shooter, was transported to a nearby hospital, CBS reported.
The president of the temple, Satwant Kaleka, was among those shot and taken to a hospital, the Journal Sentinel reported.
Carolyn Bellin, a spokeswoman for Milwaukee's Froedtert Hospital, told CNN that three victims were in in critical condition.
"We have no idea" of the motive for the shooting, one of the temple's committee members, Ven Boba Ri, told the Journal Sentinel. "It's pretty much a hate crime. It's not an insider."
Ri told reporters that, based on communications with those trapped inside the temple, the shooter was a white male in his 30s.
"It's sad, I don't know how to describe it," Ri told the Journal. "Sikhism is such a peaceful religion. We have suffered for generations, in India and even here."