Felony murder conviction reversed because the instructions given allowed jurors to convict even if defendant developed the intent to aid and abet the robbery after the act causing death. Defendant Patterson snatched a gold necklace from around the neck of an elderly woman in the parking lot of a grocery store. In the process, he knocked her to the ground, and then ran away. McDonald, who was parked near the victim’s car, picked up Patterson as he fled. The victim died an hour after the robbery. McDonald was convicted of felony murder during a robbery and other offenses. He was sentenced to LWOP and appealed, raising claims of instructional error. Held: First degree felony murder conviction reversed. To aid and abet a felony murder based on robbery, an accomplice and the killer must be jointly engaged in the robbery at the time of the act causing death. Here, when the court instructed the jury on felony murder (CALCRIM No. 540B), it omitted a bracketed paragraph that states that the defendant must have intended to aid and abet the robbery before or at the time of the act causing death. The general instructions given did not inform the jury that McDonald had to have aided and abetted the robbery before the act that caused the victim’s death in order for him to be found guilty of felony murder. CALCRIM No. 1603 instructed the jury that to aid and abet the robbery, McDonald must have formed the intent to aid and abet the crime before or while the perpetrator carried away the property to a place of temporary safety. Together, the instructions permitted McDonald to be found guilty of felony murder even if he did not form the intent to aid and abet the robbery until after the act causing death. Because the evidence did not overwhelmingly prove that McDonald aided and abetted Patterson before or during the act that caused the victim’s death, the error was not harmless beyond a reasonable doubt.