J in OP

On Tuesday, the Mariners Victor Robles made a baserunning blunder trying to steal home with a 3-0 count on the batter and bases loaded. He was thrown out at home. Bad choice. But I am hoping someone can help me with mechanics of the plate umpire, who was holding his right hand up in the air as the steal began. I would have thought this was an indication that time was out. Is it something else? I do not know how to post a screen shot, or I would post a picture of it. I am a longtime reader of this site, so I figured this was the place to go with my question! Thanks!