When I had fastened my eyes (ατενισας). This personal touch Peter adds from his own experience. See on Luke 4:20; Acts 3:4; Acts 3:12 for this striking verb ατενιζω, to stretch the eyes towards, first aorist active participle here.

I considered (κατανοεω). Imperfect active of κατανεοω to put the mind down on, to ponder, I was pondering.

And saw (κα ειδον). Second aorist active indicative, saw in a flash.