Is that actually confirmed? Does anyone recall the exact issue this is stated? Because from what I can tell that isn't quite clear yet. Does anyone know for sure?
That said... I would argue it doesn't even matter if the explosion was of Wally's own volition; the reason being it isn't even clear that Wally knew anybody was next to him when he lost control of his powers. When he does his narration of the accident in HiC #8, he acknowledges that people were walking up to him in the field... but not that he knew it at the time. That makes it an accident either way and therefore it needs no alteration. I may be miscalculating but I sense people just don't like the aesthetics of Wally's actions having killed people, regardless of circumstance or if it was his fault or not.