Fleeing suspect rams 2 police cars in Bristol, Pa.

BRISTOL, Pa. (WPVI) -- A Bucks County man wanted for armed robbery and drug charges tried to get away by ramming two police cars during a traffic stop, authorities say.

He's now behind bars.

Police in Bensalem and Bristol townships say they tried to pull over 20-year-old Christopher Hess of Bristol Wednesday.

Hess reportedly tried to flee the scene in his car and, when he couldn't, he ran off on foot.

Officers caught up with him and arrested him.

Hess is being held on $550,000 bail.