SAN FRANCISCO (BCN) — Police in San Francisco are investigating after an assault and robbery on Saturday near Union Square left a 65-year-old man in critical condition.

According to police, around 3:30 p.m., officers responded to a report of a robbery near the corner of Powell and Sutter streets.

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There, they learned a man was putting items he had just purchased into a backpack when a suspect grabbed the victim’s backpack.

A struggle ensued and the suspect then pushed the victim to the ground and punched him several times, police said.

A nearby security guard was able to apprehend the suspect and detain him until officers arrived, police said.

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The victim was taken to the hospital for his life-threatening injuries, according to police.

Officers arrested the suspect, a 52-year-old man, on suspicion of robbery, as well as for two unrelated warrants he had out of Palo Alto, police said.

He was not identified.

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