"Students have their laptops out a lot -- doing a lot of studying," said Qais Faraj, an employee at Sack's Coffee House. "People know that, take advantage of it. So we've become a target."
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There have been more than 25 laptop thefts within two months, and that has people taking matters into their own hands.
UC Berkeley student Alex Ferguson witnessed a citizen's arrest Friday afternoon. "They kind of scanned the laptop area before and they just grabbed the laptop right over here in this area and like sprinted out."
RELATED: Berkeley police use undercover sting to combat laptop thefts
Several customers chased after thieves on College Avenue.
"I think one of them had an athlete backpack on too so he was pretty quick to it," Ferguson added.
Witnesses say the laptop thief ran out of the coffee shop to a waiting vehicle, handed the laptop off, then took off down the road. So the laptop, unfortunately, was not recovered.
"I have witnessed more than five or six times myself," said coffee shop visitor Sagar Gajurel.
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The problem is so pervasive police are now going undercover in the coffee shops.
The tactic led to the arrest of six people this past weekend and police say their undercover work will continue.