Can i still use elemental hero the shinings effect if i use him to fuse with another monster?

i was playing a match today and i thought that i could cleverly fuse shining to get back 2 monsters from my rfg pile but my opponent and some spectators said that i couldnt do it because the timing was off, something about how one of the cards hits the grave first or something lol so i was just wondering if anyone knew the exact ruling to this delima? PS: I STILL BEAT HIM!!! :D