First Lieutenant Jack Mathers (ジャック・マザーズ中尉, Jakku Mazāzu-chūi) is the leader of the Hamlin Battalion 2nd company and supervises the Biological Weapons Research regiment of the Hamlin Battalion.
Jack has blonde hair that is shaved to almost bald and green eyes. He is very muscular and had brutish pig-like features along with pointed ears (Frank Mathers looks similar to him).
Jack wears a brown polo shirt with the logo of the Hamlin Battalion at the back, half-pants of regular Hamlin Battalion soldiers design (hence, there are no knee pads) with a black utility belt around his waist and green combat boots. Said utility belt is attached to his upper body by suspenders. He also wears a dark blue lieutenant hat and brown gloves. As for equipment, there are numerous case boxes on his utility belt and there is a case box on his both pant legs. He has a device which prevents the Terror Bites from attacking him on his neck. As for weapons, he is armed with two M249 para machine guns clamped together, Mk 2 hand grenades and uses Mantis Terror Bites. Even with occasionally disarmed by Captain Rush, Jack is an expert wrestler who is able to defend himself in unarmed combat and even a hit from a large wooden crate on his head did not work against him.
Mathers was once a hero in the past and extremely loyal to America. Serving Gregory Barrows, Mathers does not always listen when it comes to certain tasks (since he tends to be a fanatic type). Knowing that Barrows' orders are absolute, Mathers vows to listen and communicate with Barrows more closely. He is sent to guard the Biological Weapon Research Facility in Wyoming against those who oppose Barrows. It is unclear whether he died after the battle or merely fell unconscious and was arrested later. However, judging by the weakening of his voice, it could be assumed that he died after getting shot many times by the V.S.S.E. agents (weakening him) and punched by Captain Rush (effectively killing him).
|Japanese version||English version||Remarks|
|これ以上、我々の邪魔をするな！！||Alright, I've had about enough of you!||Jack Mathers, upon being confronted by the V.S.S.E. agents and Captain Rush|
|（ラッシュ: 貴様ら、何を企んでいる！！愛国心はどこへ行った！？）...そんな物が何の役に立つ？||(Rush: What are you trying to do? Where's your patriotism?) What good is patriotism?||Jack Mathers, answering Captain Rush's question about his patriotism before battling the V.S.S.E. agents and Captain Rush|
|（ラッシュ: 貴様も合衆国に忠誠を誓った筈だろう！）そんな昔の事は忘れたっ！！||(Rush: You took an oath of loyalty to your country!) That oath meant nothin'!||Jack Mathers, replying to Captain Rush that he knows not of loyalty|
|ホラホラ！ふらついてるぞ（ラッシュ: ...まだまだ...、これからだ...）||Uh-oh! Looks like you're almost down for the count! (Rush: No way, I'm just getting started.)||Jack Mathers, taunting Captain Rush that he (Rush) cannot get up to fight back|
|（ラッシュ: テラーバイトで何をするつもりだ？）めちゃくちゃにしてやるんだよ、この国を！||(Rush: What are you planning to do with those Terror Bites?) We're going to destroy this country!||Jack Mathers, replying to Captain Rush on what he (Mathers) wants to do with the Terror Bites|
|（ラッシュ: いい加減、目を覚ませ！！こんな反逆が許されるとで思っているのか？！）あの方の命令は、絶対だ！！||(Rush: Wake up! You really think you're gonna get away with this?) His orders are absolute!||Jack Mathers, cementing his loyalty towards Gregory Barrows to Rush|
|（ラッシュ: いい加減、おとなしくするんだ）そんな攻撃が自分に效くかぁ！！||(Rush: I'm gonna have to teach you some manners.) That attack won't work on me!||Jack Mathers' response to Captain Rush's attack|
|もう手遅れだ...||You're too late.||Jack Mathers' last words|
- His hairstyle is similar to that of his namesake, the Jack robots of the Tekken series of fighting games also created by Namco, especially to Gun Jack.
- He is the only antagonist that can talk while fighting, notably the player can shoot him when he is fighting Captain Rush but is unable to decrease his lifebar (the latter trait is first used by Giorgio Zott on his final lifebar).
- He, along with Wild Fang, is a boss that was not finished by shooting down to death (Jack Mathers was finished by an uppercut from Captain Rush).