Small towns in Southern California remained on edge Monday as helicopters and police cars searched for a former police officer suspected of killing three people, including a Riverside police officer.

Officials believe Christopher Dorner's rampage stems from being kicked off the Los Angeles Police Department five years ago.

As the manhunt entered its fourth day, residents in the nearby upscale Irvine community are growing more concerned.

"If he did come around this corner, what could happen? We're in the crossfire, with the cops right there," Irvine resident Joe Palacio said.

"I do think about where I would put my family," he continued. "Would we call 911? Would we hide in the closet?"

Dorner posted a Facebook rant against those he holds responsible for ending his career with the LAPD. The 33-year-old has gained a following of Facebook supporters, some of them praising him for fighting corruption.

Meanwhile, officials have offered a $1 million reward for tips leading to Dorner's capture.

"We will not tolerate this reign of terror," Los Angeles Mayor Antonio Villaraigosa said.