>>> we are back tonight as promised with a dramatic rescue story where witnesses saw something and said something, and in this example it paid off. it happened near dallas when two young people saw a woman signaling for help after ashe was apparently kidnapped. now she's safe, a suspect is under arrest, and the two teenagers are being hailed as heroes. we get the story tonight from nbc 's amike taibbi.

>> reporter: aaron and jamal were just two pals driving in northeast texas when they saw a pretty blonde in the back seat of an adjacent car mouthing the words "help me." arias dialed 911.

>> i'm on the highway witnessing a robbery. not a robbery. a kidnapping.

>> how did you know she was saying help me?

>> we could read her lips. i mean, we turned around to check her out, and my friend sees her going help me, help me. then while they're driving off she's just like starts hitting at that back windshield. we could see her hand and she looked frantic.

>> they stayed on the other car's tail and on the line with the 911 dispatcher for long minutes and it was tense.

>> they're far ahead of us, but i can speed up and get it. actually, oh, my god, i'm speeding up to them and they're going faster.

>> reporter: the 25-year-old woman had allegedly been forced into the back seat of her own car outside a dallas office building . her abductor getting behind the wheel and speeding off. but that 911 call triggered a quick police response. aaron and jamal watching it all.

>> oh, thank god. you guys are awesome. oh, my god, oh, my god, get him. oh, my god.

>> the suspect, 37-year-old charles louis , is now jailed on a charge of aggravated kidnapping. a knife and handgun found in the car. sheriff's deputy told nbc news she's lucky she had those guardian angels looking aafter her. a story whose ending --

>> thank god! you guys are awesome.

>> reporter: -- could have been tragically different. mike taibbi , nbc news, los angeles .