The incident happened near the parking stalls of Penn Park in Whittier just after midnight on Sunday.
According to family members, Andrea Vazquez was there with her boyfriend when an armed man approached their vehicle and started shooting at them. Her sister, Edlyn Vazquez, said the boyfriend took off but when he returned, Andrea was gone.
"As he turned his back to ask for help, in that moment, my sister was kidnapped," said Edlyn.
19-year-old allegedly kidnapped during shooting at Whittier park; family pleads for help
Police said 20-year-old Gabriel Esparza, a Whittier resident, was arrested at his job Monday in the city of Lakewood.
He has since been booked into the Whittier Police Department jail on murder and kidnapping charges and is being held without bail.
Police called this a random killing.
"At this time, it appears that Andrea Vazquez and her male companion were randomly targeted by the suspect at Penn Park," read a press release issued by police.
The body of Andrea, who was a fashion design student at Fullerton College and worked at a mall in Cerritos, was found late Monday night in a vegetation field in Moreno Valley.
Edlyn had said she was able to track Andrea's location for a few minutes shortly after the incident using Apple's Find My iPhone feature.
"I tracked it to ... going down the 60. I started following it and the location stopped in Moreno Valley, and that's the last known location that I have of her," she said.
Meanwhile, a weapon believed to have been used during the crime was recovered. Esparza's vehicle, a 2013 white Toyota Tacoma truck, was also recovered.
Police said the case will be presented to the Los Angeles County District Attorney's office on Wednesday.