A shout-out to Boston Globe photographer John Tlumacki, who snapped the dramatic photo of 78-year-old Bill Iffrig, who hit the deck after the first of Monday’s two bomb blasts near the finish line of the Boston Marathon. The image, which went viral almost immediately, says it all about the frantic, scary moments after the explosions. And Sports Illustrated seems to agree. The magazine chose Tlumacki’s pic for the cover of the issue it is racing onto newsstands. Explaining the decision to use the picture of Iffrig, SI managing editor Chris Stone said: “We felt it truly captured the horrific moment at the end of the race — there’s a fallen runner, police with their guns drawn, and loose debris from the explosion.’’ We’re told it’s the first Sports Illustrated cover with a non-sports figure — not counting the magazine’s annual swimsuit issue — since Sept. 26, 2011.