Vallejo's Police Chief said the officer mistook a hammer in Sean Monterrosa's sweatshirt pocket for a gun.
RELATED: Family speaks out after Vallejo police mistake hammer for gun and shoot, kill 22-year-old
Monterrosa's supporters rallied in San Francisco's Mission District Friday.
His family is devastated that a Vallejo police officer shot and killed him early Tuesday morning.
"She got the phone call and they say, Sean is dead. I started crying and I said we need justice," said Sean's father, Neftali Monterrosa.
That call came from Sean's girlfriend, not Vallejo police. Sean's sister says the police department didn't call her until a couple hours prior to Wednesday's news conference when Chief Shawny Williams officially announced an 18-year law enforcement veteran fired five shots at Sean through his windshield. One bullet hit and killed Sean who was on his knees at the time. His family believes he was surrendering. Chief Williams said the officer believed Sean had a gun. It turned out to be a hammer.
VIDEO: Vallejo police announce at news conference that 22-year-old killed by officer had a hammer, not a gun
ABC7 News I-TEAM reporter Melanie Woodrow asked Chief Williams during a press conference Wednesday what the rules are for Vallejo Police Department in terms of firing through a vehicle's windshield.
"The officers that are part of the crime reduction team are SWAT operators. It's a practice that they practice. It's basically the rules of law apply to when you're defending yourself. If there is a threat, a credible threat you can respond to that but they do train to shoot that way," said Chief Williams.
Chief Williams said it is allowed within the department.
It's a practice that may be scrutinized now. The California Attorney General has announced an agreement with the City of Vallejo and the Vallejo Police Department to collaborate on a comprehensive policing plan to reform Vallejo Police Department's policies and practices as well as increase public trust.
"Whatever's in the dark will come to light. I know Vallejo PD is trying to cover something up more," said Michelle Monterrosa, Sean's sister.
RELATED: Vallejo police officer shoots, kills 22-year-old on his knees after mistaking hammer for gun, chief says
The review promises improvements in use-of-force procedures, anti-bias and community policing, and accountability.
Chief Williams was asked but would not give the officer's name. He said the department has 45 days to release body worn camera video and would do so even sooner.
Here's the Vallejo Police Officers' Association's response to the fatal shooting:
The family has created a change.org petition here.
The family has created a GoFundMe to help with funeral costs, here.