This crook just wanted to work — with someone else’s tools!

San Francisco police on Friday arrested a man suspected of robbing a construction site in Mission Bay, cops said.

A security guard at the Third and Mission Rock streets site responded to a motion sensor alarm, police said. While investigating the alarm, he saw the suspect standing in the work zone carrying a bag of tools and a tool box. The crook saw the guard and fled.

Cops arrived around 1:30 a.m., got a description of the thief and combed the area. A cop assisting the search saw a man at Fourth and Mission Rock streets who was “breathing heavily and sweating profusely,” cops said. A bag of tools were by his feet.

He was detained by police and the security guard identified him as the thief. A background check revealed he was on felony probation for burglary and narcotics, cops said. He was arrested and booked at Bayview Station.

rnagle@sfexaminer.com