Max sentence: Life without the possibility of parole
Max fine: $10,000 (Source 1, 2, 3 and 4)
The California penal code defines first degree murder as "willful, deliberate, and premeditated killing," or any killing that occurs during during the commission of another crime, such as arson, rape, carjacking, robbery, burglary, mayhem, kidnapping, or train wrecking. Basically, the kind of stunts you pull for fun without a second thought in GTA is guaranteed to be first degree murder in the real world. This one's a biggie: offenders face 25 years to life, or life without the possibility of parole (yikes!) if the murder is deemed a hate crime or, weirdly, if the person you murdered was operating a public transportation vehicle like a bus or train. It gets worse if you use a gun or are associated with a gang, and other circumstances can even upgrade you to the death penalty, at which point the crime is classified as capital murder. Basically: don't kill anyone.