Primeval

A forensic anthropologist is looking over a mass grave of people who have been killed by what she claims are identical gunshot wounds. Both the woman and the UN soldier head away from the mass graves to inspect another one on the south side. She digs her shovel into what she believes is another mass grave only to be attacked by an unseen creature. The anthropologist is dragged into the water as the UN soldier opens fire. Other soldiers show up and begin shooting at the attacker as it devours the woman and heads for deeper water.The next setting is a New York City news room. The main character, Tim (Purcell), is seen and he is looking at a TV and talking on his phone. Apparently he is waiting to see if his name is mentioned in connection with a case that he was working on. Not much is heard about this. His cameraman and best friend Steven is telling him maybe their boss, Roger, did not see or hear what was being broadcast on the news. Right when he says that Tim is asked to see Roger, which Steven says was really quick and jokes about being a cameraman for another reporter. Tim then goes to see Roger who in turn does not want to talk about his contract just yet but instead introduces him to a very attractive woman standing by another television set viewing a report about the woman who was seen previously with the creature. This is where Gustave is introduced. The woman's name is Aviva and she is a reporter that focuses on reports dealing with animals being killed or harmed, and she is interested in the crocodile who is known to have killed hundreds of people in Africa. Tim is more-or-less "forced" into going to Africa with her and brings Steven along to help capture this creature.In Burundi they meet Harry, who is there to warn them about "The Bush," as he calls it, and the dangerous warlord who lives there, who has nicknamed himself "Little Gustave." They are to travel via riverboat to their destination, a small village, where they will set up their traps in attempts to capture Gustave. All attempts to capture Gustave fail. Their cameraman, while getting scenic video, catches on film Little Gustave himself executing the village people who helped the group. The guards that are sent with the group end up working for Little Gustave. Both of them get killed either by gunshot or Gustave.Then a fast-paced series of events takes place. The group tries to kill Gustave with a hand grenade resulting in the death of their guide and their crocodile expert that went with them. A helicopter appears and it looks like the survivors are going to be rescued. But Little Gustave's men attempt to blow up the helicopter to stop them from showing the video of the execution. That results in the group getting separated. Steven gets separated from the group and Gustave chases him. We don't find out happens to Steven till later. The other members of the group come together to look for Steven but Aviva has to stay with the injured Jojo. Tim finds Steven's camera. Little Gustave (who is actually Harry) comes to get the video himself. That results in Aviva, Tim and Jojo getting captured. Tim attempts to trick Little Gustave by giving him the GPS locator that tracks Gustave by saying it tracks the suitcase that also has a copy of the video. Little Gustave declines and forces Tim to find the suitcase. That's where they finds Steven's body. Aviva splatters pheromones on Little Gustave and Gustave comes and kills Little Gustave. Tim, Jojo and Aviva escape to the range rover and Gustave appears and attempts to kill all three but they manage to escape. We see the group on a plane home. The ending states that the civil war ended and Gustave is still alive and killing.

Question: Who chases Steven?
Answer: Gustave