B.C.'s police watchdog has been notified after a man suffered serious injuries falling from a Burnaby apartment suite late Thursday night.

The RCMP said officers with the Emergency Response Team and Burnaby detachment entered the Sanders Street building at around 10:40 p.m., believing a kidnapping victim was being held inside a unit on the 11th floor.

Residents heard the commotion as the officers raided the unit.

"It was two of the loudest bangs I had ever heard," said Jason Matthews, who lives on the fourth floor. "I moved into the stairwell and there were about 6 officers in S.W.A.T gear, and they told me to go back and that there was no fire."

Police typically use flash bangs, also known as stun grenades, to temporarily disorient suspects.

When the officers walked into the home, three men allegedly tried to escape over the balcony – and one ended up falling to the ground.

"While two men were arrested without incident on lower floors, one man fell to the ground and suffered serious injuries," Sgt. Janelle Shoihet said in a news release.

The alleged kidnapper fell just inches away from a woman's balcony railing on the first floor and landed in a bush.

"There were at least 10 people working on the guy, one of them was holding his neck. He fell several storeys," said Tina, who did not want to disclose her last name. "They worked on him for 10 minutes and then they put him in an ambulance."

All three suspects remain in police custody, one in hospital recovering from his injuries. The apparent kidnapping victim was found safe and "physically unharmed," Shoihet said.

Burnaby RCMP said it notified the Independent Investigations Office so the watchdog can determine whether officers' actions or inactions contributed to the one suspect's injuries.

The IIO is tasked with investigating any police-involved incident that results in death or serious injury.

The police watchdog did not disclose the victim's age, sex or whether they knew the three suspects.