This dear priest was the chaplain at my secondary school and I had quite a few dealings with him as he helped the Sr. train me and several others up to be extra-ordinary ministers of the Eucharist. Given the time he passed it's so likely he's gone straight to Heaven, so instead I ask for prayers for the parishoners, especailly children, who witnessed this. His family also.
Strangely, he's not the first priest I know of who's died at Mass, a few years back in the same diocese a priest died moments before Midnight Mass on Christmas. He was sitting in his vestments already to go and then just went to sleep in the Lord.