Cambridge Police are thanking an “astute” taxi driver who helped police catch a man chasing a college student with a knife in Cambridge Thursday night.

Authorities said Abdi Yusuf, 53, put a knife to a throat of another homeless man and demanded his cup of change.

The victim complied, and as Yusuf left, police said he demanded a passing college student’s money as well.

When the second victim fled, Yusuf allegedly gave chase, screaming at her and brandishing a knife.

When officers arrived at the scene of Mass Avenue and Plympton Street after a detailed report from a taxi driver witness, they were able to find Yusuf, who had allegedly had a knife visibly sticking out of his pocket.

Police said he complied with their commands and was placed under arrest.

His charges were not immediately available.