The one thing that I would add ....
When things have calmed down, you might want to have a talk with your son to assure him that it is okay to call 911 if there ever is a true emergency. You wouldn't want him remembering the upset and embarrassment and hesitate to make that call.
Emergencies are tense situations. The one time our family needed to call 911, I -- as an adult -- could not bring myself to do it. I called a nearby friend instead and it was he who told me I needed to call 911.
About once a year we cover emegencies with our 8-year-old Cub Scouts. We talk about what kind of situations would be a good time to call 911, and what will happen if they do ever need to call 911 -- What the 911 operator might say, the kinds of questions they might be asked, that they will probably be told to stay on the phone and keep talking until help comes. We tell them that if they are not sure, to call 911 and the 911 operator will know whether to send help now or help them know who else to call. (I should have followed that advice myself - at least it turned out fine and the delay was not to critical.)
We have them prepare a list of emergency numbers to put by their phone: Mom's work, Dad's work, a nearby relative or trusted neighbor. Sometimes we get into discussing that there is another number to call the police in non-emergencies...
We also assure them that it is not likely that they will have to call 911, and if they do, there is likely to be an adult present to call instead, but we just want them to know what to do.
In your son's favor, should he ever need to make that call, he now knows he won't need money to do so!