The Red Sox had already taken a 2-0 lead on CC Sabathia and the Yankees in the first inning of their series finale in Boston Sunday night when Alex Rodriguez, hitting fifth for the Yankees, led off the top of the second against Ryan Dempster. See above for what transpired.
That GIF shows Dempster's first pitch, which was behind Rodriguez's legs, and his fourth, which hit Rodriguez in the left elbow. The two pitches in between were also balls inside, but not close enough to hit Rodriguez.
Home plate umpire Brian O'Nora immediately, and demonstrably, warned both benches, prompting Yankees manager Joe Girardi to fly out of the dugout and into a rage. His fit was presumably about Dempster not being thrown out immediately for clearly throwing at Rodriguez, though possibly about how the Yankee bench was warned as a result of Dempster's actions. Instead it was Girardi who was tossed, the only person on either team to have been run as a result of the incident.
Rodriguez had no overt reaction to the plunking, but the Yankees rallied after the hit-by-pitch to tie up the game. In his next at-bat, which proceeded normally, Rodriguez drove in the go-ahead run without a groundout to put the Yankees ahead, briefly, 3-2.
Thus far, with the game in the fourth inning, there have been no further incidents.
Update: In his third at-bat, Rodriguez led off the sixth inning with a solo home run to straight-away center off Dempster. The blast pulled the Yankees to within 6-4.