B.C.'s police watchdog says it is investigating an officer-involved shooting in Maple Ridge.

The Independent Investigations Office confirmed on Twitter Sunday afternoon that it is investigating a shooting involving police in "Ridge Meadows."

.@iiobc has been notified of an officer-involved shooting in Ridge Meadows. Further details will be released when available. — IIOBC (@iiobc) August 11, 2019

The incident took place in Maple Ridge, at a home near the intersection of 124 Avenue and Colemore Street. A large police presence could be seen at the scene.

What exactly transpired between the arrival of police officers and the shooting is unclear. Neither Ridge Meadows RCMP nor the IIO had commented on the specifics of the case as of Sunday night.

Thant Din told CTV News three members of his family lived in the home. One of them, his 54-year-old brother Kyaw Din -- who he said went by the name John -- was shot and killed by police officers on Sunday, Din said.

He said his brother had a mental illness that often left him in and out of hospital. Sometimes, he said, his brother would stop taking his medication. When that happened, his sister -- who also lives in the Maple Ridge home -- would call police to have him taken to hospital.

On Sunday, Din said, his brother didn't want to go with police when they arrived. According to Din, his sister asked officers to wait for other family members and a translator to arrive.

Din's sister Yin Yin told reporters she met with police when they first got to the home.

"They asked me if my brother has a gun," she said. "He doesn't have a gun. He doesn't have a knife. He's just in the room and I told the police he has a glass bottle that he might throw at you. I don't want you to get hurt and I don't want the police to shoot my brother."

She said police reassured her that they wouldn't hurt him, but she was still worried.

"Police said, 'We would never shoot your brother. We deal with this kind of thing all the time,'" she said.

And yet, she says three gunshots rang out almost immediately when police went into her brother's room.

"For no reason, they shot him," she said. "Can you imagine? Brother was doing housework in the morning and now he is dead."

Thant Din told CTV News his brother was sometimes loud and confrontational when not taking his medicine, but he said Kyaw never became violent.

"He never hit anybody," Din said. "He might be screaming and yelling, but he never hit anybody."

The IIO is a civilian oversight board tasked with investigating incidents involving police officers in British Columbia that result in death or serious injury.