12/30/2014 12:06 EST | Updated 02/28/2015 05:59 EST

New video of mentally ill man who was shot by Vancouver transit police

New surveillance video is shedding light on a man's mental state before he was shot by police in Surrey, B.C. on Sunday. 

The 20-year-old man can be seen in the video pacing inside a convenience store. According to the store clerk Connie Yong, he demanded a knife. 

"He was looking for a knife and I said I don't have a knife," she said. 

"He was so focused on looking for a knife, something sharp. I thought he was going to get the sharp stuff and then kill someone."

Prior to going into the convenience store, the man was seen screaming and banging his head against a wall at the Surrey Central Skytrain station. After not finding a knife at the convenience store, the man went to a nearby Safeway.

Witnesses say the victim stole a knife, walked towards the bakery and stabbed himself repeatedly. Police tried to de-escalate the situation, but he was shot and died of his injuries, the IIO said.

The agency, which provides civilian oversight of serious police incidents, said it will review the convenience store surveillance tape as well as 911 audio and postmortem exams. 

According to Vancouver police, about eight people are arrested daily under the Mental Health Act, and between 30,000 to 40,000 calls they receive annually involve someone who may be mentally ill.

Earlier this month, a man was arrested for threatening to kill police officers under the act. He was later released without charges. 

In November, another mentally ill man was shot and killed by an officer in South Vancouver. At the time, Vancouver police said Phuong Na Du, 51,  was distraught and waving a 2-by-4.

He refused to comply with officers' directions and bean-bag rounds were fired in an attempt to disarm him, according to police.