The Running Man

In 2017, after a worldwide economic collapse, American society has become a totalitarian police state, censoring all cultural activity. The U.S. government pacifies the populace by broadcasting game shows where convicted criminals fight for their lives, including the gladiator-style The Running Man, hosted by the ruthless Damon Killian (Richard Dawson), where "runners" attempt to evade "stalkers", armed mercenaries, around a large arena, and near-certain death for a chance to be pardoned by the state.
Two years later, Ben Richards (Arnold Schwarzenegger), a police helicopter pilot wrongly convicted of a massacre during a food riot in California, escapes from a labor camp and seeks shelter at his brother's apartment. He finds it is now occupied by Amber Mendez (MarÃ­a Conchita Alonso), a composer for ICS, the network that broadcasts The Running Man. Richards asks Mendez about the whereabouts of his brother, and she says that he was taken for "re-education", possibly hinting at his fate.
Taking Amber hostage, Richards attempts to flee to Hawaii, which is now a separate state, but she alerts airport security and Richards is captured and taken to ICS. There, Killian tries to convince him to participate in The Running Man, saying that if he refuses, William Laughlin and Harold Weiss, members of a resistance movement that Richards had met, will be forced to participate instead. Reluctantly, Richards agrees, but learns that Killian had enrolled Laughlin (Yaphet Kotto) and Weiss (Marvin J. McIntyre) as runners anyway.
As the game begins, Richards and his friends are attacked by the first stalker, "Subzero" (Charles Kalani, Jr.), but they fight back, with Richards killing Subzero â the first time a stalker has ever died on the show. Laughlin and Weiss search for the network's uplink facilities, which they realize are in the game zone. Amber sees a falsified news report on Richards' capture and, suspicious of the media's veracity, does some investigating. She learns the truth about the massacre of which Richards was convicted, but she is captured by her own ICS colleagues and then sent into the game zone.
The runners split up, each pair pursued by a different stalker. "Buzzsaw" (Gus Rethwisch) critically wounds Laughlin and is killed by Richards. Weiss and Amber locate the uplink and learn the access codes, but "Dynamo" (Erland Van Lidth De Jeude) finds them and electrocutes Weiss. Amber's screams lead Richards to her, and as the two evade Dynamo, the stalker's buggy flips, trapping him inside. Refusing to kill a helpless opponent, Richards leaves Dynamo alive as the studio and home audiences watch. He and Amber return to Laughlin who, before dying, says that the resistance has a hideout within the game zone.
Back at ICS, Killian sees Richards' popularity growing, with viewers betting on him to win instead of the stalkers. Off-camera, Killian tries to offer Richards a job as a stalker, but when Richards refuses, Killian sends the next stalker, "Fireball" (Jim Brown), after him and Amber. Fireball chases them into an abandoned factory, where Amber discovers the decomposing corpses of the previous seasons' "winners" â realizing that they were killed by Fireball and their victory was faked. Fireball goes after Amber, but Richards rescues her and kills him.
Frustrated and running out of options, Killian seeks "Captain Freedom" (Jesse Ventura), a retired stalker, to kill them. However, when Freedom refuses, the network creates digital body doubles of Freedom, Richards and Amber, which are then used to fake their deaths on the live screen. In the game zone, Richards and Amber are captured and taken to the resistance's hideout, where they learn of their "deaths". Using the access codes, the rebels get into ICS' control room, broadcasting footage that exonerates Richards and reveals the truth about the game's previous "winners". As Richards heads to the main studio floor, shocking the audience who had watched him supposedly die, Amber fights and kills Dynamo, the last remaining stalker.
Richards confronts Killian, who has by now lost credibility. Sven (Sven-Ole Thorsen), his senior bodyguard, deserts him, having grown tired of Killian's antics. Killian begs for his life, saying he created the show to appease the U.S. love of reality television and televised violence. In response, Richards decides to give the audience what they want â by sending Killian to the game zone in a rocket sled. The sled hits a billboard and explodes, killing Killian to the delight of the audience. Richards and Amber share a kiss as they walk out of the studio.

Question: Who attacks Richards and his friends?
Answer: the first stalker