The suspect opened fire on a school police officer Wednesday in Woodland Hills, prompting a lockdown at nine schools.
The Los Angeles City Council approved on Friday the maximum amount it can offer, $75,000. Several police and fire associations added $15,000 and the founder of the 99 Cents Only store chain donated $9,999.99.
"We want the public to be alert that this individual is a threat to all of us," said Los Angeles City Councilman Dennis Zine. "He's armed. He shot at a uniformed police officer. And this reward is very important to keep the public attention on this until this individual is apprehended."
Authorities are hoping the reward, combined with a composite sketch of the suspect, will soon lead to an arrest.
The gunman is described as Caucasian, in his mid-to-late 40s, 5 feet 9 inches to 5 feet 10 inches tall with a thin build. He had long, gray hair that was tied in a ponytail.
Los Angeles school police officer Jeffrey Stenroos was gunned down outside El Camino Real High School. He was shot in the chest, but his protective vest saved his life.
A U.S. Coast Guard Auxiliary member who witnessed the shooting rushed to the officer's aid, using a police radio to call for help.
"What I did, I don't feel was anything that unusual. I'm a member of the Coast Guard Auxiliary. What I did [Wednesday] was just do what I'm trained to do," said Michael Brody.
Anyone with information was urged to call the Los Angeles Police Department at (877) LAPD-24-7. Callers can remain anonymous.