Double Foul

[commish]

I have been a basketball official for nearly 30 years but saw a new situation last Thursday. 3 person crew at the boy's varsity level: A 20 drives to the basket on a transition break-away on Trail-Lead side. There is a massive collision as A20 makes the basket over defensive player B15. Lead calls a charge on A20 and Trail simultaneously calls a block on B15. After consultation, they come out with a double foul and wipe off the basket. Is it possible to have a double foul in this situation - how can you have a charge when the other player blocked? How can you have a block when the other player charged?