Califano was remembered as a great friend and family man.
He was killed last Friday night when a truck slammed into the rear of his police cruiser on the Long Island Expressway in Old Westbury, N.Y.
Officer Michael Mullen worked with Califano. He says it's not guns or other violence, but routine traffic stops, which pose the most danger to police.
Mullen called the 12-year veteran and married father of three boys a warm-hearted guy and great family man.
The truck's driver, 25-year-old John Kaley, is charged with criminally negligent homicide and assault.
Kaley, of New Britain, Connecticut, was held without bail after his arrest, but a judge Tuesday set bail at $47,500. Defense attorney William Petrillo said his client's thoughts are with the officer's family. He said the crash was accidental and not a crime.
Investigators say Kaley had fallen asleep behind the wheel. He suffered minor injuries, as did his fiancee, who was riding with him.
The National Highway Traffic Safety Administration says drowsy drivers cause more than 100,000 crashes every year. The toll is more than 1,500 people killed and 40,000 injured.