CROWN HEIGHTS, BROOKLYN — New Yorkers will rally on the corner where Saheed Vassell, a man who reportedly suffered from bipolar disorder, was shot dead by police who mistakenly believed he had a gun.

Hundreds of people are expected to rally on Utica Avenue and Montgomery Street where Vassell, 34, was shot dead by NYPD officers responding to 911 calls at about 4:40 p.m. Wednesday, according to the rally's Facebook event page. "Saheed Vassell, an unarmed Black man was murdered by NYPD Wednesday night," NYC Shut It Down organizers wrote. "Join us as we demand justice for Saheed Vassell. Black Lives Matter!"

Five officers — three plain clothes and two in uniform — fired 10 rounds at Vassell after receiving reports that he was waving a gun at people walking on the street, according to NYPD Chief of Department Terence Monahan. The officers saw Vassell take "a two-hand shooting stance" and point what was later revealed to be a metal pipe with a knob at the end of it, Monahan said.

Vassell died later that night at Kings County Hospital, police said. Now organizers from NYC Shut It Down — an activist group against formed in response the deaths of Eric Garner and Mike Brown — plan to gather where Vassell was killed to speak out against a police response family, friends and witnesses say was unnecessarily violent.

"[Vassell would] just walk around the neighborhood and help people," his father, Eric Vassell, told the New York Times, adding that his son was the father of a 15-year-old son and suffered from bipolar disorder.

Witness Jaccbot Hinds, 40, told the Daily News that the officers jumped out of an unmarked police car and fired at Vassell without giving him any warning.

"It's almost like they did a hit," Hinds said. "They didn't say please. They didn't say put your hands up, nothing." And Fee Andrews, a local who said she's known Vassell for 12 years, questioned why he had been shot repeatedly.