Following the mutant attack he tries to buy time for the other survivors, managing to take down one mutant. Mark is then shot and killed by Bug. Soon after Bug commands a group of mutants to feed on his corpse.
Mark seemed to have been something of an anti-thesis to Rusty. While Rusty is selfish and only really concerned for himself (at least in the early scenes) Mark is much more of a team player, looking out for the whole group of survivors.
Mark doesn't seem to have had any particular relationships.
Mark seems to have had no notable abilities.