Angela Aguilar had just gone back inside her Fullerton home to cook. She thought her 6-year-old daughter, Grace, was also inside.

Grace Aguilar, though, was in the front yard, where she had gone to sit by her favorite tree. Angela Aguilar heard the crash, but she didn't realize that an out-of-control driver had struck her daughter.

Grace Aguilar died in that Feb. 17 crash, which police say was caused by a drunk driver, and now her parents can only look back on a young life that had filled theirs with so much joy.

"For something so stupid to happen in a second, just to have (your child) taken away from you, it's not fair," Angela Aguilar said. "It's not fair."

Immigration officials say 50-year-old Maximino Delgado Lagunas, who is in the United States illegally, had a blood alcohol level nearly three times the legal limit when he was arrested. Immigration and Customs Enforcement has revealed to NBC4 that Lagunas, a Mexican national, had been deported twice, once in 2001 and again in 2008.

Court records show that in 2015 he was arrested for another DUI. Immigration officials say that back then Buena Park police did not detain Lagunas for the required 48 hours for pickup by immigration officials, instead placing him on informal probation and releasing him to the streets.

Angela and Jesus Aguilar say it took them eight years to have a child. Now they can only mourn their daughter after Lagunas' actions.

The girl's parents say their daughter was friendly and mature. She loved people, nature and God. Her father remembers her hugs and her smiles. Her mother remembers the sound of her voice.

"She had this beautiful laugh," Angela Aguilar said. "I still hear it in my head every day."

Lagunas could now face a possible murder charge.

"He's taken away from me the best thing I had in life," Jesus Aguilar said.