OAKLAND -- Andrew Barrientos said, in a confession to detectives, that he did not know he was shooting at a police officer when he critically injured a plainclothes Fremont officer who was trying to arrest him.

But the 20-year-old's mother told police hours after the shooting that her son called her in a "rushed" state just minutes after the incident and said, "I just (expletive) up. I just (expletive) up. Mom, I shot a police officer."

The mother's statement to police was just one of many new tidbits of information revealed in public for the first time Wednesday during the first day of a likely four-day-long preliminary hearing against Barrientos and two friends, Gustavo Silva, 23, and Francisco Sierra, 30, who are accused of helping him escape.

All three Union City residents have pleaded not guilty.

Barrientos is charged with more than a dozen felonies, including attempted murder, for shooting Officer Todd Young in August in what police said was an attempt by the suspected gang member to escape arrest for an outstanding warrant.

His mother's statement to police was introduced as evidence Wednesday afternoon as she begrudgingly took the witness stand in the case against her son.

Although Andrea Barrientos, 44, gave police a detailed recounting of the conversation she had with her son moments after he is accused of shooting Young, she said in court that she did not remember anything.

She said she was too traumatized by the events that occurred after the shooting to remember specific statements.

"I don't recall what was said. I remember that he called me, I picked up, he said things and all I remember him saying is, 'I'll call you back,' " she said. "He said he loved me and 'I'll call you back.' "

In her recorded statement to an Oakland homicide detective, Andrea Barrientos described a detailed conversation that ended with Andrew Barrientos admitting that he knew he shot a police officer.

"My son called me, he just said 'Mom, I (expletive) up, I (expletive) up,' " Andrea Barrientos is heard saying on the recording. "I said, 'What did you do?' He said, 'Mom, I shot a police officer.' "

Andrea Barrientos' statement to police was introduced as evidence by deputy district attorney John Brouhard after he provided the court with a text message conversation she had with her son before the shooting.

In that conversation, Andrea Barrientos told her son that she had begun to save money to hire an attorney for his defense should he be found and arrested for an outstanding warrant.

"I'm so worried about you," she wrote in the text message. "You just know that I will have your back to the fullest."

Andrea Barrientos admitted on the witness stand that she knew her son was wanted in connection to a high-speed chase and said she urged him to turn himself into police. But, she said, he refused because "his priority was his baby because the baby was sick and he wanted to be with his child."

Other than being notified by her daughter that her son had a warrant, Andrea Barrientos said that she really did not pay attention to what her son was doing with his life. Although she said she kept in constant contact with her children through text messages and phone calls, she said her son "keeps his business, his business."

She appeared to be a reluctant witness and frequently looked at her son throughout her testimony, and both grinned at each other whenever they made contact.

Her lack of memory about certain events also appeared to frustrate Alameda County Superior Court Judge Thomas Reardon who, after peppering her with a host of questions, declared that she had been "willfully evasive."