Gregory Elarms, 58, has been charged with first-degree murder for allegedly fatally shooting David Lewis as he got out of his car at the shopping center June 9.
The district attorney's office has additionally charged Elarms with illegal possession of a firearm, and a special circumstance of lying in wait, which would make him eligible for the death penalty.
At his arraignment this afternoon, Elarms delayed entering a plea and was assigned a court-appointed attorney.
He is scheduled back in court Jan. 4.
Elarms is believed to have followed Lewis from the nearby San Mateo Medical Center, where he was conducting HIV testing and counseling.
"We have reason to believe that Mr. Gregory Elarms killed David Lewis in cold blood," San Mateo police Chief Susan Manheimer said at a news conference Monday.