LOS ANGELES -- For over two decades, all Maria Mancia had of her son was a single photo, a slightly blurry image of a boy, 18 months old, staring unsmiling into the camera.

On Thursday, he was wiping away her tears at a reunion neither of them ever expected.

When the boy's father abducted him from their Southern California home in 1995, he also took every picture she had of him, even the ultrasound of him during her pregnancy. She had to write to a relative just to get one picture to show the police.

But early this year a tip led investigators to Mexico and the son, Steve Hernandez, now a 22-year-old law student.

On Thursday morning, he came to the U.S. and immediately met his mother.

"It was a shock," Hernandez told the San Bernardino Sun. "I didn't know if she was alive or not and to get a call that says they found my mother and that she had been looking for me, it was like a cold bucket of water. But it's good. It's good."

The two parents and their toddler boy had been living in Rancho Cucamonga, California, in 1995. The parents were having relationship struggles. Mancia came home from work one day and thought they had been robbed. It took her a while to figure out that both her son and his father were gone.

The San Bernardino County District Attorney's Child Abduction Unit had been looking for Hernandez for years, searching for him in several states.

Investigators then received a good tip in February that he was in Puebla, Mexico. The father, Valentin Hernandez, is missing and believed to be dead, authorities said.

Senior Investigator Karen Cragg, who led the search, said they had to approach Steve Hernandez delicately, and at first used a ruse.

"We didn't want him to know what was going on," Cragg told The Associated Press on Thursday. "We didn't want to scare him off. We weren't sure what the circumstances were down there. We had to tread very carefully."

They told him they were investigating his missing father so they could interview him and get a DNA sample. The facts fit what they knew of the missing boy.

Cragg then asked the Department of Justice if they could hurry on the test, knowing it could take several months.

"They called me in two weeks and said it was a match," Cragg said.

Cragg and her partner Michelle Faxon drove straight to Mancia's house.

"It was like she didn't believe us at first," Cragg said. "She began to cry. She said she couldn't believe he was still alive."

Because Steve Hernandez is a U.S. citizen, there were no immigration troubles returning him to the U.S., Cragg said. Authorities in both countries were hugely helpful in making it happen.

The boy's father had told him that his mother abandoned the two of them.

He also has four younger siblings he knew nothing about, including an 8-year-old brother who came to the reunion but mostly hid behind his mother.

He said he plans to stay in the U.S. and hopes to attend law school, which he already started in Mexico.

He hugged his crying mother when he finally met her, and wiped tears from her eyes.

"Now this anguish I've carried is gone now that I have my son back," she told KABC-TV. "I spent 21 years looking for him not knowing anything."

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Associated Press Writer Amy Taxin contributed to this story from Santa Ana, California.