They're doing a decently good job of staying alive so far, Martin thinks, but also instantly pushes those thoughts off so as not to incur Problems.

"I'm-- I'm not leaving you here with this thing!" Like yes, he would prefer not to be here, but if Mercy got hurt or worse from this and he took off the guilt would eat him alive. "I'm only running if you're also going to run!"

In the meantime, he's just going to continue pelting it with rocks and sticks he finds on the ground. Helping! Mostly.