CHICAGO (CBS) — Chicago Police want to use a high-tech tool to keep an eye on big crowds and big demonstrations: aerial drone cameras.

But civil libertarians are pushing back, warning the eye in the sky could be more of a spy in the sky.

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CBS 2 political reporter Derrick Blakley reports.

The proposal was sparked by last year’s Las Vegas massacre where 58 were killed by a single shooter.

“Las Vegas had bought drones, and after the event they found the drones had been sitting in boxes,” said Illinois State Senator Martin Sandoval (D-Chicago.)

The Las Vegas shooter also had Chicago’s Lollapalooza festival in his sights.

Sandoval wants Chicago Police to have drones overhead keeping watch over big crowds, whether gathered in Grant Park, in Soldier Field or elsewhere.

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“I believe law enforcement should have every possible tool to protect public safety,” said Sandoval.

But the American Civil Liberties Union wants police drones banned at political demonstrations.

“Law enforcement never says ‘we want to use this new technology to spy on people.’ They always say ‘we want to use this new technology to keep you safe,'” said the ACLU’s  Karen Sheley

Just what can police observe using a drone camera? Opponents claim they can see plenty, especially using facial recognition technology which authorities can employ to identify specific individuals.

Activist call it chilling, because the same drone that can provide breathtaking pictures can do other things.

“(It) allows the government to collect lists of people who are engaged in free speech activity,” said Aren.

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But the Illinois Senate has already approved the bill and it’s now on its way to the Illinois House.