Police say Alfred Olango was fatally shot Tuesday after he quickly drew an object from his pocket and pointed it at an officer in a "shooting stance."
Police say they were responding to a report of a mentally unstable man.
It turned out Olango was holding an e-cigarette device with a barrel-like tip.
There were peaceful protests in the first nights after Tuesday's shooting, but on Thursday night some protesters threw bottles, one threw a brick at police officers and others pushed a man off his motorcycle. Authorities say five people were arrested.
El Cajon Police Chief Jeff Davis says authorities decided to make the video public after protests over the shooting became increasingly violent. Police have released two videos.
The videos show the officer almost immediately firing when the man suddenly raised both hands in what has been described as a shooting stance.
Another officer who just walked up fired a stun gun.
Davis says Olango's family was invited to watch the video footage before it was made public but declined the invitation and he does not know why they declined.
A lawyer for the family says the video shows an officer provoked the man before opening fire and they claimed the image had been "cherry-picked" to support the police version of the shooting.
(The Associated Press contributed to this story.)
