"He's getting aggressive," said Capt. John McGinnis, commanding officer of the Northeast detectives, "and he's probably going to end up hurting somebody."

McGinnis described the suspect as a Hispanic male, approximately 20 to 30 years old, 5-4 to 5-8, with a thin build. He has green eyes and a Spanish accent.

The gunman has primarily robbed stores, including Rite Aid, Dollar Tree, Auto Zone, and Wine and Spirits shops, mostly in the Northeast, and also in parts of Port Richmond and Fishtown, usually around closing time.

McGinnis said the gunman typically walked into the stores wearing a black ski mask and/or gloves, with a large black duffel bag slung over his shoulder. He then herded employees to the back at gunpoint and told them to tie themselves up with ties or duct tape. At some point, he locked the stores' front doors and demanded that the managers open their safes, sometimes threatening to kill people.

Before fleeing, the gunman warned the victims not to call police for at least 20 minutes.

McGinnis noted that the robberies have escalated in frequency and nature since three were reported by police in January. In total, there have been 16 robberies, 12 in the Northeast area, and four in the nearby suburbs, with four committed in the Northeast in April. The last robbery was on April 24 at the Wine and Spirits on the 11000 block of Bustleton Avenue.

In the early robberies, the gunman first cased the store, McGinnis said. Now, he "comes right in and takes over the store."

And he carries two guns instead of one.

"He's getting pretty good paydays," McGinnis said. "We don't know if he's a drug addict, but he seems to be getting more and more desperate as the robberies go on."

In January, when police released information about the robberies, McGinnis said they didn't receive a single phone call. Now he's imploring the public once again to phone tips to 215-686-3153.

"This is a very dangerous individual," he said. "If anyone knows anything, they should call police."