Timecop

By 1994, time travel has been developed and is used for illicit purposes. The Time Enforcement Commission (TEC) has been established to police the use of time travel, with Senator Aaron McComb overseeing operations. Police officer Max Walker has been offered a position with the TEC but is unsure whether or not to accept. While at home with his wife Melissa, he is attacked by unknown assailants and witnesses the house explode, killing her.
Ten years later, Walker is a veteran of the TEC working under Commissioner Eugene Matuzak, who sends him back to 1929 to prevent his former partner, Lyle Atwood, from using knowledge of the future to financially benefit from the U.S. stock market crash. When confronted, Atwood admits to be working for Senator McComb, who needs the funds for his upcoming presidential campaign. Fearing that McComb will erase him from history, Atwood attempts to jump to his death, but Walker catches him mid-leap and returns to 2004. Refusing to testify, Atwood is sentenced to execution and is returned to 1929 where he resumes falling to his death.
Walker is assigned a new partner, TEC rookie Sarah Fielding, and together they are sent back to 1994 to investigate McComb. They witness a meeting between young McComb and business partner Jack Parker, where McComb wishes to withdraw over a disagreement about a new computer chip. They are interrupted by the older McComb, who arrives from 2004 to stop the exchange claiming the chip will become highly profitable. Older McComb specifically tells his younger self not to touch him as the same matter cannot occupy the same space, and then kills Parker. Fielding turns on Walker, revealing that she works for McComb, and after a shootout Fielding is wounded and Walker escapes back to 2004.
Walker returns to the TEC to find the future altered. McComb is now sole owner of the computer company and is a presidential front runner while the TEC is being shut down due to budget cuts. Walker appeals to Matuzak, who has no knowledge of the alternate present. Matuzak sends Walker back to the past in a prototype time machine, sacrificing himself in the process.
Back in 1994, Walker finds Fielding in the hospital and after interrogation she agrees to testify against McComb, though she is murdered in her room shortly thereafter. While at the hospital, Walker finds a record of a recent visit by his wife Melissa, discovering that she was pregnant. Realizing that she would be killed later that night, he tracks her down and reveals himself to be from the future.
That night, the younger Walker returns home and is attacked just as before, with the assailants revealed to be in McComb's employ, but is unknowingly aided by his older self who has been lying in wait. With the assailants defeated, the older McComb steps in and takes Melissa hostage, confronting the older Walker with the bomb. Walker then reveals that he had previously lured the younger McComb to the house, who enters the room. After McComb wounds Melissa, Walker pushes the two McCombs together and, as the same matter cannot occupy the same space, they merge together into a liquefied mass before disappearing from existence. Walker then escapes with Melissa before the bomb explodes and lays her down beside his unconscious younger self before returning to the future.
Back in 2004, Walker finds the timeline changed for the better. Matuzak and Fielding are alive and active in the TEC, whereas McComb no longer exists. Walker returns home to find Melissa alive and waiting for him with their 9 year old son.

Question: Who sacrifices himself to send Walker to the past?
Answer: Matuzak