Orange County sheriff's officials took the suspect, identified as Samuel Lincoln Woodward, into custody on Friday.
Orange County District Attorney Tony Rackauckas said during a press conference that charges were pending against Woodward and did not elaborate on what he could face until all details of the case were looked over.
Investigators also said they would not release details of the condition of Bernstein's body or what may have occurred at the park.
Woodward and Bernstein knew each other from high school, but authorities did not provide details on the nature of their relationship.
When news of the arrest came out, Jeanne Pepper Bernstein, the victim's mother, responded to ABC7 reporter Greg Lee with a statement.
"Revenge is empty. It will never bring back my son. My only hopes are that he will never have the opportunity to hurt anyone else again and that something meaningful can come from the senseless act of Blaze's murder," her statement said, in part.
Finally. My thoughts are: Revenge is empty. It will never bring back my son. My only hopes are that he will never have the opportunity to hurt anyone else again and that something meaningful can come from the senseless act of Blaze's murder. Now Do Good for Blaze Bernstein— Jeanne Pepper (@bernsteinmom) January 12, 2018
Bernstein's body was found Tuesday after heavy rains revealed some of his remains in a shallow grave in the brush along the perimeter of Lake Forest's Borrego Park, authorities said. Investigators said they were looking into his death as a homicide.
The University of Pennsylvania student was last seen entering Borrego Park at about 11 p.m. on Jan. 2 by Woodward, who was with him at the time.
MORE: Search warrant provides new details into investigation of OC student's death
A search warrant, which has since been sealed, recently revealed details of the investigation.
An affidavit described detectives' interview with Woodward, who drove Bernstein to the park the last time he was seen alive. Authorities also believe the pair drove to multiple locations before going to the park.
Woodward said he and Bernstein spoke on Snapchat that night of Jan. 2 and made plans to pick him up. According to the document, Woodward said Bernstein seemed depressed, but didn't say he wanted to hurt himself.
They drove to the park, and then at some point, Woodward said Bernstein then walked alone into the darkness.
Bernstein didn't respond to messages, so Woodward said he left and went to a girlfriend's house, then returned to the park later.
Bernstein was reported missing the next day. His parents said he left the house with no wallet, money, identification, keys or eyeglasses.
Authorities did not provide any details into a motive for the crime.