MESA, Ariz. -- Mesa police tracked down a robbery suspect by using DNA from his shoe he left behind.

Officers said Donnie Ahmed robbed a man on May 18 in a parking lot using a BB gun.

Ahmed struck the victim with the BB gun causing lacerations on the victim's nose and left cheek, police said. As the victim yelled for help, Ahmed grabbed the man's watch, wallet and food, police said.

When he took off, he dropped the food and left behind a shoe, investigators said.

Officers said DNA matched a known sample from Ahmed.

Ahmed was arrested on June 30. Police said he admitted that he robbed and assaulted the victim.

Ahmed also confirmed that he slipped out of his size 12 shoe as he was fleeing, officers said.

Ahmed was booked on charged of armed robbery and aggravated assault.