LOS ANGELES (CBSLA) — A young man who was being robbed fought to keep the gold cross his grandmother left him, and was killed for it.

Authorities are stepping up their efforts to find the pair investigators believe robbed and shot 22-year-old Rene Lupian, who had been walking home from a shift at an In-N-Out Burger in Pico Rivera on Nov. 7, with a $20,000 reward for information leading to an  arrest and conviction.

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“My brother was loved so much by so many people,” his sister Christina Lupian said at a news conference.

Surveillance video showed a woman walking near Lupian in a liquor store just before he was attacked. A composite drawing of her and a male suspect were released by authorities.

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A gold cross that the victim wore around his neck on a chain – a keepsake left to him by his grandmother – was found on the ground where he died. Authorities believe Lupian given up his backpack, but had been fighting to keep it the gold cross.

Lupian had a promising future – he studied literature at Antioch University and enjoyed writing poetry and music, and had just applied to a trade school to pursue his dream of becoming an architect, according to Los Angeles County Supervisor Hilda Solis. She had recommended the reward for information on the gunman.

Anyone with information about the murder can call sheriff’s homicide Detective Theo Baljet at (323) 890-5500 or make an anonymous tip to Crime Stoppers at (800) 222-TIPS (8477).

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(© Copyright 2018 CBS Broadcasting Inc. All Rights Reserved. City News Service contributed to this report.)