A gun was recovered from the Birmingham flat where a man was shot dead by police, investigators say.
Trevor Alton Smith was killed by a single shot when officers raided his home in Wheeleys Lane, Birmingham, at about 05:00 BST on Friday.
Officers said they were following up an "intelligence-led operation" concerning possession of firearms, the Independent Office for Police Conduct (IOPC) said.
No-one else was in the flat at the time.
Officers attempted resuscitation on the 52-year-old who went into cardiac arrest, but Mr Smith was pronounced dead at the scene.
The police watchdog said it was reviewing officers' bodycam footage which is believed to have captured the shooting.
IOPC Commissioner Derrick Campbell said: "My understanding at this stage is it has captured everything that took place during the incident - including the shot - that's my understanding.
"We are viewing the footage to see what takes place."
Six firearms officers had gone to a block of flats in Wheeleys Lane, Lee Bank, to carry out an arrest.
Mr Campbell said West Midlands Police "notified my office just before 6am that an officer had discharged their weapon and someone had been shot".
Mr Campbell said the IOPC was carrying out a "thorough" investigation and forensic material was being collated and analysed.
"We have made contact with Mr Smith's family to explain our role and I send them my condolences for their loss, and my thoughts are with everyone affected," he said.
"I can assure people we will carefully examine the circumstances of the shooting along with what planning went into the police operation.
"I would ask everyone for patience while a thorough investigation is carried out."
West Midlands Police and Crime Commissioner David Jamieson said he scrutinised "police use of force very closely" and was monitoring the situation.
It is the second fatal shooting by West Midlands Police this year.
The IOPC is investigating the death of Sean Fitzgerald who was killed by armed police in an operation in Coventry in January.
The previous fatal shooting was in 1996, the force said.
It is the fourth time the force has deployed a firearm since 2017, when ex-gang member Sharif Cousins was shot in the chest in an alleyway in Rubery.
Mr Cousins survived and was the first person to have been shot by a West Midlands Police officer since 2000.
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