From the article -> “He was responding to a deputy who was inquiring whether the fire investigation had been completed. Since Wood was acting within the course and scope of his duties when he began to type his response, under Vehicle Code section 23123.5, he acted lawfully.”
So by this same logic - if he was typing on his computer and rammed his car into a McDonalds and killed 10 people, this would have been lawful too???
If I'm not mistaken, if you do a first act lawfully, and you do a second act like reckless driving as a result of the first - you're still liable for the second act. If you drink a coffee lawfully and spill it on yourself and then jump lanes and hit a bicyclist - you don't think you'd get hit with vehicular manslaughter?? And your argument would be, "I was drinking coffee lawfully, so lets throw this case out of court?"