San Bernardino County Sheriff's Department Deputy Lawrence Falce. File photo: San Bernardino County Sheriff's Department / AP

San Bernardino, California - A 70-year-old, off-duty sheriff's deputy braked to avoid two dogs and was rear-ended by a driver who then got out and delivered a fatal punch, police said on Wednesday, announcing a murder charge against the man.

The attack occurred on New Year's Eve and San Bernardino County Sheriff's Deputy Lawrence Falce was taken off life support two days later.

Surveillance video from a nearby store captured the encounter, which lasted only about a minute. After the fender-bender, Falce and a man police identified as Alonzo Leron Smith got out of their cars, exchanged words and motioned at each other. Smith then delivered a single punch to the face and Falce fell backward, his head hitting the pavement.

San Bernardino Police Chief Jarrod Burguan said: "We believe that he was knocked unconscious almost immediately and he never did regain consciousness."

Smith got back in his Ford Explorer and the video showed a truck ramming it to try to keep him from driving off. Smith managed to drive away but was arrested hours later, police said.

Gang member 

San Bernardino County district attorney Michael Ramos said the 30-year-old San Bernardino man was a gang member who had spent much of his adult life in jail. He was released in 2015, after serving two years of a 12-year sentence for selling marijuana. Smith pleaded not guilty on Wednesday to murder with special circumstances.

"This person needs to spend the rest of his life in prison," Ramos said. 

San Bernardino County Sheriff's Department spokeswoman Cindy Bachman said Falce was the oldest member of the 3700-member force, which does not have a mandatory retirement age but requires deputies to pass training exercises several times a year to ensure they still can do the job.

"He spent all of those years basically patrolling the community he lived in," she said.

Sheriff John McMahon said Falce had worked 36 years as a deputy sheriff, and also coordinated search-and-rescue volunteers.

"He was a mentor and a great partner to countless deputies who had the privilege to work with him," he said.

Falce is survived by his long-time girlfriend and a sister, the sheriff said.