BROOKLINE (CBS) – Boston University students are being warned after two were robbed at gunpoint in Brookline. Investigators say the culprits used an interesting technique to figure out if the pair had phones.

They asked a simple question: “What time is it?”

These days to answer that question many people don’t look at their watch, they take out their phone. Once that happened the victims were held up at gunpoint with a semi-automatic weapon.

It happened around 3am Sunday near an alleyway on Thorndike Street. They took money and two cell phones; a Droid and an iPhone.

The victims were not hurt.

Students in the neighborhood just off Commonwealth Ave say word is spreading to be careful that smartphones are a potential target for thieves

Brookline Police say they can’t be exactly sure what the robbers were after but the victims say the suspects did ask them what time it was before making their move.