Phoenix Police released the surveillance video Saturday in hopes of catching the thief.
But they also wanted to track down the other man in the video, the Good Samaritan.
The victim told police she didn't get a chance to thank her hero.
After the video aired on FOX 10, one valley woman recognizes her son as the Good Samaritan in the video.
Tyler Salas may seem like an ordinary 19-year-old man, but he's the mystery man behind an extraordinary act of courage.
In surveillance video from the McDonalds, you see Salas chase down the robbery suspect who had assaulted a child.
"I would of really, really regretted it, and hold a grudge on myself if I didn't do anything," said Tyler Salas.
Salas said he was in the drive-thru at Burger King at 35th Avenue and Van Buren when he noticed the suspect next door in front of the McDonalds confronting a woman walking with a 3-year-old boy.
Salas said the man snatched the woman's purse. During the struggle, the 3-year-old was pushed to the ground, causing his front teeth to be knocked out.
"As I was approaching the lady, that's when I noticed the boy was bleeding, I was like don't worry little man, you're going to be all right," said Tyler.
Salas stayed on scene until the women left to get help.
But, she told police she never got her hero's name. Salas says he was just doing what he would want to be done for his mother.
"I'm proud that he did what he did," said Kim Salas.
"I felt the right thing to do was return what was stolen, I would do it all again if I could," said Tyler.
Phoenix Police now will work to connect the victim and her hero.
Meanwhile, police are still looking for the suspect.
The suspect is described as six feet tall, 35-years-old, and approximately 175 pounds.
If you see him you are urged to call Phoenix Police or Silent Witness at 480-WITNESS.