MIAMI (CBSMiami) – An anonymous tip led police to the man they say used rocks to rob a man at the Metrorail station across from the University of Miami last month.

Desmond Jackson, 24, has been charged with one count of armed robbery.

On January 14th, Humberto Lopez Mata was standing on the ground level at the University Station when a man, later identified as Jackson, came running straight at him, according to police who added he was armed with two rocks.

The two struggled as Lopez Mata, 39, tried to hang onto his Kindle and the iPhone.  Lopez Mata eventually realized they weren’t worth his life and let them go.

Lopez Mata did try chasing his attacker, but was slowed down by the locked fare gate.

The surveillance video shows the thief running up the stairs and then back down.

He eventually dropped the electronics he swiped.

Cops were able to locate them using GPS technology on the phone.

At the time of the robbery the station was not deserted, security video shows several people walking around including several children running. Investigators believe Jackson watched and waited until the coast was clear before catching Lopez Mata off guard.

Acting on a tip, Coral Gables police arrest Jackson at 6260 SW 63rd Avenue on Wednesday. Lopez Mata identified him as his attacker when shown a photo line-up.

Jackson is being held on $7,500 bond.