It started, as most things involving Steve do, with a fight. Sam was one of the closest to the fight in New York, so he was quite quick and ready to get there. But what made the call out interesting was that Steve was saying someone else from the 40s had just shown up. As Sam was making his way through the skyscrapers to where the fight was going on, he was making a mental list of some of the people that it could have been. Any one of the old Howling Commandos, possibly one of the Justice Society...there's a rather large list.

So when Sam finally gets into range, he sees that the fight is mostly over. Looks like a quick mop up would be needed, but Sam, flying in as fast as he could, could easily make that a reality. He sees Steve punching out a goon, as well as someone he didn't know. He was guessing they were the friend of Steves.