A jury convicted the passenger, Robert Darrell Johnson, 36, of first-degree murder. But that same jury later decided the killer was insane at the time of the stabbing, meaning Johnson would not go to prison for the crime.
Kester family members, who attended the trial daily in San Bernardino Superior Court, are outraged, confused and frustrated.
"This is a real horrible thing," said Barbara La Clair, Kester's mother-in-law. "I was thinking about making a sign and standing out in front of the court - just so people would know. It would read `the killer that stabbed the Omnitrans bus driver 18 times is walking the street."'
Lawyers confirmed that Johnson would not spend time in a prison cell. But he will not be a free man either.
"He will likely be sent to a state mental hospital," said defense co-counsel Andrew Moll, adding that Johnson could serve a maximum life sentence at a locked, secured facility where he will likely receive treatment and therapy.
Johnson is scheduled to return to court on Jan. 11, when a judge will decide which facility he will go to.
"If someone is found to have been restored to sanity, they could be moved to a different facility with lower security," Moll said. "But that is so far in the future.
A convicted killer deemed insane is sent to a state mental facility for treatment, according to state law, said prosecutor William Lee.
At some point during his treatment, Johnson could be deemed sane again. And if that's the case, he could be released.
"That scares us," Lee said. "That's why we pursued the fact that he should go to prison. We felt he was sane enough to be responsible for the crime."
La Clair, 69, of Fontana, echoed those thoughts.
"That is a scary thing that this guy will be out back on the streets," she said. "He's not crazy. He's sane."
But his lawyers disagree. They say his theoretical release is a long ways away.
"In Johnson's case, and from what came out in trial, it is highly unlikely, even impossible," Moll said. "This was an individual diagnosed as far back as when he was 18 (years old). He was involuntarily hospitalized 26 times. He has a deep-rooted mental illness."
On May 7, 2010, Johnson boarded an Omnitrans bus near Riverside Avenue and Base Line in Rialto and walked to the back. A few minutes later, he came up front started stabbing the driver, authorities said.
Kester lost control of the bus and it crashed into a tree.
Johnson ran off the bus and into a Bank of America where he threw the knife away, authorities said. He then ran across the parking lot to a Stater Bros., where he was arrested.
Kester, 47, died from multiple stab wounds.
"The crime itself, that he did it, was rather easy to prove," Lee said about Johnson. "It was on video.
"The issue came down to his sanity."
Jurors convicted Johnson on Nov. 27. On Dec. 5, they found him not guilty by reason of insanity.
During the trial, five mental health professional testified about Johnson's competency.
His diagnosis, which was fairly consistent, was a combination of schizophrenia and mood disorders, said another Johnnson defense attorney, Erin Alexander.
Johnson had ongoing delusions in which he thought he was being hypnotized, she added, and leading up to the stabbing, his hospitalizations had been more frequent and longer in duration, Alexander said.
"He is as mentally ill as anyone I've ever represented," Alexander said.
But Kester's wife, Misty, disagrees.
After sitting through the trial, she said she believes her husband's killer was sane at the time of the crime - and that he planned it so he would look crazy.
"I don't care whatever the case is," Misty Kester said. "I think a person should pay for what they've done."
Johnson is currently medicated and is "very remorseful about what he did. It is very difficult for him to understand why he did it," Alexander said.
And Misty Kester is left deeply affected.
"My mind won't rest at ease," said the 41-year-old Fontana resident. "I don't sleep well at night. I haven't had a normal sleep since the trial."
Misty Kester said she is uncomfortable with the idea that Johnson could one day be out of custody.
"I don't feel safe," she said.
The couple had been married for 12 years. They had six children together and Lawrence Kester had two other children from a previous marriage.
Her husband, Misty Kester said, was a hard worker and a good father.
"He was a bus driver for 15 years. He loved the Lord. He would read the Bible to the children," she said.
Along with the jury, Misty Kester and her family watched the graphic video that showed their loved one's death.
"He was a good person," she said. "Nobody deserves to die like that."
Despite the outcome, Misty Kester said she is happy Johnson's trial is over.
"But I still have to live every day knowing that he's only going to a mental hospital," she said.
Reach Lori via email, call her at 909-483-9378, or find her on Twitter at @IEcourtsNow.